2 7800GTX's would definitely be FASTER than a single 7800GTX 512.
that being said, a single card does have an upgrade path, if you have insane amounts of money. in my opinion, i think if you're willing to spend THAT much money on a graphics card you should wait a few months and get the next generation ones.
2 7800gtx will be less than 1 gtx 512... last i checked the 512 was 999 at zipzoomfly, and out of stock, the gtx 256 was 400ish?...
I know it's cheaper than the GTX-512 which more than 50% above it's MSRP, but the new cards should be cheaper than that. I agree 2xGT is better and cheaper than 1 GTX-512, but the new X1900 series should be cheaper, and depending on G71 production it should be significantly cheaper too.
Just seems so ridiculous that we're still recommending the 2XGT as a 'value' solution.
If you want a card now and dno't want to wait for the 7900 series i would highly recomend the GTX 512 in every aspect , price proformance everything if you check the benchamrks the GTX 512 and the 256 in SLI are very close in almost everything , the pricing is $400 for a GTX256 and $650 for the GTX 512 http://www.actbuy.com/details.asp?item=EV10X7800GTX-3
the only issue is getting one in stock, if you want to go all out i would recomend the black pearl
this single card goes batter than the OC'ed ASUS extream and turbo force
In fear is slumped back a bit but in other tests you can see that the 512 is comparable to the 256 in SLI i would go with that if i had the money ...sadly i gave a single 7800GT but it handles anything i ask of it
i recommend a x1900xt/xtx... the is faster than a single 7800gtx 256, in just about every test, and the 1900xtx is faster than a gtx512 i believe, plus there not as rare and even cheaper if u can find one, but if u have somthing aganist ati then the 7800gtx512 will make u very happy, as long as you can find one... id recommend a single card over sli due to the fact that sli is unreliable, by this i mean in some games sli runs great, and in others its very slow for unknown reasons (bad drivers maybe? i duno) u can see this in hl2 the most i believe. plus sli is more or less in beta stages, things arnt guarenteed to run correctly..... this is simply what ive heard about them, im not saying sli is bad im just saying its a newer tech and we all know about new stuff, wait to buy till all the bugs are worked out... since its been a while since it was released it could be much more stable now... in certain games tho single 512 runs faster than sli 256
You (right now) can get a HiS X1900XTX for around $620 free shipping, or a NewEgg has a Saphire X1900XTX for under $600 retail.
That is cheaper than two SLI 7800GT's and faster, plus you can add CF later if you want.
Or spend $520 and get an X1900XT, still faster, and better video.