What resolution are you gaming at? This is the biggest factor to look at when upgrading or going to SLi. If the res is lower than 1280X1024 you may not see that much difference.
What games are you playing? First Person Shooters usually see more gain from SLi and higher end gpu's.
I haven't used SLi myself so I'm not sure if you need the exact same card.
Check it out, and pass it along. You will not find a monitor this good that is this cheap anywhere, period. The reason I stepped out on a limb and bought it was because it had so many rave reviews everywhere I looked.
I have really enjoyed it and would buy 2 more if i needed them.
With that said, I mostly play Oblivion right now, and Im trying not to play anything else while I wait for LOTROnline to come out. I play in 1680x1050, with my CPU reaching 51 C under load and my GC sitting at 70 - 75 C under load.
So do you thnk I will see a jump? And are these cards gonna get alot hotter considering they are now gonna be right on top of each other, with a Creative X-fi sound card right below them?
I was playing Oblivion wiith the 7600's in SLI and noticed a definate improvement, I was able to turn on extra options and the gameplay was much smoother, it did still slow down a bit when there was a lot going on but it was definately much better, I was only able to play at 1280x1024 because of my monitor though.
As far as heat goes, in my setup the second card only ran about 3c hotter than the top one and I only had passive cooling (Gigabyte Silent Pipe II), neither card went over approx 65c at any time, even with ambient temps of over 35c here in the Summer, I was quite impressed with the cooling on the Gigabyte cards actually, only problem was they took up alot of space.