SLI Worthwhile?

I'm wondering if anyone can give me a general idea of the improvement I'd see between one and two GTX 280's, running with a 3.0 GHz Core 2 Duo and 4 gigs ram (haven't decided on DDR2 or 3, but my understanding is that it's not very important for performance). Has anyone done benchmarking of something comparable to this? I'm really looking for anything that would let me decide whether I should get a second card or not for my new build (and whether it would even be worthwhile to add one later, or better to just replace the card when I need to upgrade). Basically, how much of a real boost is SLI.



PS, while I might at some point, assume for arguments sake the system I described is NOT overclocked.SLI Worthwhile?
I haven't experienced SLI, but I game at 1680x1050 and considered slapping another GPU in my system and all the advice I get is that at that resolution (or lower) SLI isn't really worth while. SLI Worthwhile?
If you have a SLI board, then it's a cheap upgrade road for good enough performance.
I can't speak for that particular card, but I have done benching with mine and they scale very well depending on the game and drivers. For example I experienced a 100% increase in frames for UT3 and around a 60% or 70 % in CoD4. Using the latest drivers and comparing single card to 2xSLi I saw about a 80% increase in 3Dmark score.
Put i this way, SLi is way better than it used it be and I only expect it going up from here, and the latest drivers from Nvidia not only give boosts in performance but also utilize Agiea Physx processes using the GPU all the more reason to have more horse power in that area.
It was never, unless you play on a 30'' 25**x16** or whatever that resolution is and you want to max all your games. You'll have to spend the dough for $600 cards in SLI all the time. What resolution? Also you'll need to OC that CPU to avoid bottleneck.
Pay two times the amount for 0%-40% increase....semms simple to me!Also its only worth getting if you have a very large monitor.
[QUOTE=''Daytona_178'']Pay two times the amount for 0%-40% increase....semms simple to me!Also its only worth getting if you have a very large monitor. [/QUOTE]0-40%? Maybe that was years ago, SLI performance is better today.
I'm debating picking up a second 8800GTS 640mb, I can get a recertified one for $100... or just waiting for Q1 to see what 40nm offers.