The cost is roughly the same, so what should I purchase? Dual GTS(320) or single GTX?

what resolution do u play ?
i were in the same situation like u and i go for 8800gtx and i am loving it , i suggest u getting the 8800gtx

In cases where SLI is functional and scaling well then two 8800gts will outperform a single GTX. The VGA charts on the Tom's front page are a good resource to look into this in more detail. http://www23.tomshardware.com/graphics.html

The general rule is that the best single card you can buy is always favourable to sli/crossfire because of the inconsistent performance.

If you have the best single card you can buy and because of high resolutions the performance is still unacceptable then a second card is the next logical step.

It depends, generally as as already stated many times on the forum, a single faster card is better than 2 lessor in SLI. What do you run, and what resolutions do you run at?
SLIing 2 next step down cards can be slightly beneficial in some games if you run at very high resolutions on a large monitor (22"+). Otherwise, get the 8800gtx. It will outrun the SLI'd GTS's in most every other situation.

2 cards for the same money as 1 card does not equal better performance.

A rule of thumb I think is pretty good to follow about SLI.
Always buy the single fastest card you can afford at first. A year later, when the price on the card has dropped, and you start feeling the need for a little boost, then grab another one and go SLI.

Besides the fact that a single GTX is a lot better than SLI GTS in terms of performance (most games) and performance consistency (SLI is not predictible), the GTX will generate a hell of a lot less heat and use a lot less power too.

Go with the GTX, no doubt. Have one card you can be proud of than two crippled GTSs humming away in your case. Also, doesn't the game have to implement SLI effectively to get better performance than 1 GTX?

well, not if you SLI GTS 320... cause they still will have 320 MB RAM (per chip) and in such case they just won't perform in very high resolutions

my opinion is, that SLIing 320s is useless, they will theoretically be faster in lower resolutions, but then you have CPU bottlenecking the system. and in higher resolutions they will lose to GTX because of the amount of RAM they hve. as someone noted - get GTX, less problems, less heat and better upgrade path (you can always add another one later)

Here's my view on this. SLI GTS's may provide slightly better performance than 1 GTX. But that 1 GTX dishes out incredible performance on it's own. If you already have the SLi board, you can then pair 2 GTX's latter on. IMO, buy the best card that you can afford now and double it up latter when you can afford or want to.

Ooh, Sli'd 8800GTX's. *drools uncontrollably*

How do you figure that a 8800GTX will not be as hot as a GTS?? I own two of each and i can tell you for a fact that the GTX's run hotter than the GTS's.

Not true.

True.

just check the charts and benchmarks for the games you want to play (and if you are looking to the future, I can't imagine they won't optimise crysis for sli)

the most imporant thing is the resolution he plays @

One GTX will run cooler than 2 GTS' crammed into a case.

Resolution has a lot less to do with it than you keep banging on about, my Sli'd 7900GT's make their presence felt at the 1280x1024 that I game at dude. s'true.