I have been busy researching my dream pc and the various components that I would like to include.  One particular spot where I keep getting hung up is on the graphics card.
 
I have never had a SLI configuration before and am curious to know some of your real world experiences on with such a configuration.
 
The premise of my question is this:
 
8800GTX card $566
 
8800GTS (620 mb) card $369 each  ($738 for 2)
 
Would it make sense to buy 2 8800 GTS and put them in SLI configuration rather than buying a single 8800 GTX?  The cost difference between the 2 GTS and 1 GTX is about $172.
 
In theory 2 GTS would give you much better performance than a single GTX and enough performance to last for awhile as new graphics cards are release so that I wouldnt have to jump at the next "big" card to come out.  
 
I have seen various 8900 series rumblings in various forums as well so I want to make a good buying decision and maximize my direct x 10 experience without minimizing my wallet...
 
Thanks for the help!

SLi for anything now is a no-go. A 8800GTX by itself does in fact beat 2 8800GTS's in SLi. The 8900's will obviously have a little more oompf than its 8800 predicessors when those are launched. If your really caught between it now and need a graphics at this time, then ONE 8800GTX is the way to go.

8800GTX

Well for the most part hardcore enthusiasts with money will go for the high end 8800GTX SLI. With that you're talking about 1600x1200 full quality here. So depending on your budget and resolution and you're quality standards on gaming, having to choose with a low to mid end card would be a good choose. The 8800GTS 320Mb, based on the reviews performs with minor difference as to compare with the 8800GTS 640Mb. But on the price, it does have a major difference as 640Mb cost around $80-$100 against it's "lower end" model.  
 
So for you, it's better to have one 8800GTS 320Mb for now. And if you still want more horsepower then get a second one. So it would be wise to pick one for now or wait just a bit for ATI's counter-attack that could be cheaper and better than the 8800s and for sure it will bring down the price for Nvidia having to compete with another DX10 card.  
 
Comparison with 8800GTS 640Mb and 8800GTS 320Mb.
Click here for the link

Where can I find benches for an 8800GTX vs 8800GTS-SLI? I had the same question as the OP but didn't find any info on it.

 
That is not true.
 
2x 8800gts > 1x 8800gtx especially at high res.

what resolution will you use, i found that at lower resolutions SLi can be better because it allows for higher AA, but it will put out lower framerates, but if its 150fps instead of 180, does it matter?

http://www.guru3d.com/article/Videocards/416/

Out of the two I'd certainly go with the GTX setup. Buying two GTS's to SLI them would be a waste as you would only be accessing the memory total of one of the cards. Its a forgotten fact that doubling up cards does not double up texture memory.

just buy the one gtx now.  if you really want to try out SLIi then wait to see what new cards are released and if they better 2 GTX's. if not then you can buy another one at a later date.  that way you can spread the cost out a bit.

just go with one gtx it should work fine.

 
Thats the 320mb version.

Did some digging and found a great article at techreport.com that actually benches G80s in SLI.
 
Personally I'll go with a single 8800GTX and add in a second at a later time when I actually 'need' it.
 
Also, this only matters if you have a monitor capable of handling resolutions like 2560 x 1600. Lower resolutions require less and less power as you scale down.
 
TechReport G80 SLI Article

I'd go for the solo GTX
 
A creative solution would be to buy a eVGA GTX now, keep the 172$ difference, and then step-up to the 8900 with eVGA if it comes out in less than three months.

Thanks to everyone for their thoughtful replies. It appears that the consensus would be to go with the one 8800GTX so I am going to make that the plan.
 
Thanks again for your help!

one thing to note from the techreport article darktide posted.  as is so far been the case, 1 next gen card will equal 2 current gen cards like mine.
 
  true i have got a good bit of life from mine and the cost was spread over a few months but as you can see,  even 2 x1950's in xfire can be equaled by one GTX.  it would be best to get one as unless the 8800 gets a long life till the next gen cards come out, it may not be cost effective to get SLi especially GTS's.
 
EDIT: never read your last reply correctly and would appear this post is useless.