current PC specs:
 
EVGA X58 SLI3
i7 2.66 with Cooler Master V8 CPU Fan
3 GB DDR3 SDRAM 1333 MHz
Zotac GTX 295
1000 watt Ultra PSU
Cooler Master 932HAF full tower
Vista 32bit
 
Just ordered: Win7 64bit Home Premium + 3 x 4 GB Corsair Vengeance 1600 MHZ
 
i7 extreme is crazy expensive, so perhaps I could upgrade the video card, but the GTX 690 is also crazy expensive.
 
A while back you guys gave me some good advice concerning the GTX 560 I had bought to replace my GTX 295.  As a consequence, I took the time to save the 295 with a good cleaning, and I've been enjoying it since.  As a bonus, I was able to get a refund for the 560.  Back then, the 560ti was recommended as a replacement, and today it was also suggested to me on another forum.
 
I remain unconvinced, but I'm still looking for actual benchmarks. A comparison page found on google, only says the GTX 295 should be theoretically better.  At any rate, I can buy a GTX 295 used for cheaper than a new 560ti.
 
What advice can you give me on the following questions:
Do I have the system I need to gain from 2 x GTX 295?
Will I need a bigger PSU?
Can I mix video brands (like Zotac & EVGA)
What would help me load HD textures faster?
Are there many big commercial 3d games that don't support a SLI profile?
 
Please suggest any better $200 upgrade options.
 
Edit:
 
lol. The links I posted were stripped leaving the text a mess. 

People have kept their X58's for the newer GTX680's, you're fine in terms of not having to upgrade the platform.  However, the possibility exists that you will benefit from learning to overclock your CPU rather than buying a faster model.  Those who kept X58 with GTX600 have their i7's overclocked to 3.8-4.2GHz.  You already have a decent cooler, available guides should allow at least 3.6GHz so you really won't have to upgrade the CPU.
 
In about a week or so, nVidia will finally debut GTX660 Ti, a 150W card around $249-299 with the performance of a GTX570 which slightly faster than one GTX295.  You save on power, heat and get more Vram per GPU; GTX295 has 896MB per GPU since they don't add in SLI, while GTX660 Ti has 2GB per GPU, more than the 580 base model.
 
GTX295 is slightly slower than GTX480 and GTX480 is closer to GTX570, all have 480-cores total, except the later generations have higher shader frequencies and more Vram per GPU, so they'll feel faster.  Those telling you GTX560 Ti would match GTX295 assume you'll overclock it there, otherwise it isn't matched.  Though leaked specs show that GTX660 Ti may be faster than GTX580 depending on the game.  There might be a non-Ti version of GTX660 for cheaper than $249, but it may be out afterwards.

Thank you.  Waiting to buy the GTX660 Ti is a good plan.
 
But... The X58 was built to handle 3 video cards.  If I added 2 more 295's, will I achieve anything more than a massive amount of heat?  I'm curious to try because it would be like running 6 video cards!
 
Does overclocking have the potential to 'wear out' the CPU?  Maybe I should buy a fresh one to experiment with and keep the old one as a spare.

A 295 is faster than a 560 , even if its the Ti model. Except you get DX11 with the 500 series card. I scored a 295 recently here on the forums for cheap and if you can also you should go for it. If you really want an upgrade, you're going to be looking at a 580, 660, 670, or 680 etc. Your 295 should be very close to 480 and 570 level performance. Mine is at least, I had a 295, 480, and 690 all at once before I sold the 480s and the 295 was literally on par with it on most games.
 
Either get another 295 for cheap or sell your current 295 and look into a 660/670. Basically a 670 should be equal to two 295s almost in performance and you get DX11. 660 should be more cost effiecient and offer just as good performance.
Btw you talked about your board supporting 3-way sli. That doesn't apply to the 295s. They're dual-gpu cards, so if you have two 295s, you're already doing quad-sli. If you got something like a 660/670, you can do tri-sli.

ssj92
..Except you get DX11 with the 500 series card....

FYI, after a recent update of Vista and the Nvidia drivers to version 301.42, the DirectX Diagnostic tool and the Nvidia Control Panel reports that I am running DX11 with my GTX295, even though the same system information page in the Nvidia Control Panel reports the card only supports DX10.  I definitely did not install any hacks and my games are running smoothly, so I have no idea what's up with that, other than support may have recently been added by Nvidia.
 

ssj92
Either get another 295 for cheap or sell your current 295 and look into a 660/670. Basically a 670 should be equal to two 295s almost in performance and you get DX11. 660 should be more cost effiecient and offer just as good performance.
Btw you talked about your board supporting 3-way sli. That doesn't apply to the 295s. They're dual-gpu cards, so if you have two 295s, you're already doing quad-sli. If you got something like a 660/670, you can do tri-sli.

I think I will eventually replace everything, so instead I'll keep the 295 for when all the parts are available to rebuild the original system.
 
So are you saying that if a 2nd GTX295 is added, the motherboard will only support half of it?  Is there a single GPU card that can SLI with the 295?  Is there a motherboard that can fully support 6 GPUs (i.e. 3 x gtx295)?
 
Thanks for you insight!

Vista supports DX11 if there is a DX11 card. While your os supports DX11, your card is running everything at DX10. 
 
Now your board will do two 295s(thats quad SLI because 1 295 = dual gpus sli'd already) and there is no way to do 6 way sli. With three 295s only two would be running games while the third one would be doing nothing. Now if you got a single card like a 660 Ti, you can run three of them in triple-sli. 

Thank you for the clarifications.  In the last benchmark chart pointed to, I noticed that the gtx690, was not included.  I also didn't realize how much AMD was kicking butt. Where would 2 x gtx660ti be represented in the chart?
 
 

690 and newer cards: 
 
http://www.overclock3d.net/reviews/gpu_displays/evga_gtx690_review_including_quad_sli/7
 
as for the 660 Ti, its faster than a 580. So one 660 Ti would be faster than your 295 by a bit. It shouldn't be too much slower than a 670. 

I notice that a GTX690 SLI, is not much faster than GTX 690.  One has got to have money to burn to go for that little extra.
 
Until the gtx660ti is released, it may be impossible to know, but will anyone hazard a guess at what would be the reasonable equivalent single card versus 2 x gtx660ti?  A gtx680 is almost double the price, but may be worth it if it can beat 2 x gtx660ti. 

My opinion? Buy a 580 for ~$230 shipped used here, sell the 295, and then upgrade your RAM to 6-12GB. 3GB isn't enough for some games, so that may be an issue. You'll also want to OC your CPU to around 3.8GHz or so to alleviate bottlenecks.
 
The 660Ti's in SLI should beat a single 680 by a fair amount.

660Ti will be $299, faster than a 580, no need to buy older hardware, and it will be new not used. 3GB is plenty of ram for most games, especially if the op gets rid of vista and gets 7. But 4gb+ would be good, 6Gb(3x2GB) kits shouldn't be too expensive. CPU can be clocked at 3ghz-3.20ghz and be fine. Mines is at 3.20Ghz and I'm running a GTX 690 fine without bottlenecks. At stock speeds a single card up to the 680 should be fine without bottlenecks. 660s will beat a 680 yes.
 
Also the reason two 690s don't seem to add much is because some games limit the framerates you can get and also quad-sli scaling still needs work. 

Well, I'll have more ram in about a week with a new OS.  The beauty of the 660ti, is that it's better than the 295 and I can add 2 more later.  If I can keep system improvements to $200-300 shots, I'm happy.  Buying another CPU to overclock also falls into this price range.
 
Thank you.  That pretty much answers all my questions at the moment.
 
 
 
 

You're cpu is fine and you can overclock it later, as long as you have enough cooling.