SLI does have draw backs. Benchmarks tend to always favor SLI, as they always pick games that SLI well, and only compare FPS. What they don't compare is sometimes there is a loss of image quality. They don't compare games played in windowed mode (SLI/CF doesn't function in windowed mode). They don't mention the games that don't use SLI (it's not a lot of games, but there are some). They don't mention that SLI/CF will sometimes drop out of SLI/CF without you knowing (not too common, but happens).
If you use an SLI/CF, it won't be as simple as a single card. If you don't mind always fiddling with your system, then it's fine, but I'd recommend you choose a card to SLI/CF that you could feel ok with running as a single card, as you will be doing that on occation.
Nice stuff, if you already have one gts 450, might as well get a second, IF your feeling the need for more speed . Have you tried overclocking your 450 at all ?
What resolution are you gaming at ? SLI works best at 1920x
I'll post this here for others that might be interested:
Experience GeForce with EVGA GTS 450!
EVGA is offering 150 people across the globe the chance to try out our GTS 450! You can try it out for 30 days in your own system and see how you like it, then send it back at no expense to you. For those that can't live without the new card, you can keep it for only the collateral and you don't even have to pay for shipping! Whether you want to add a 2nd card to try out SLI, or upgrade your older card - now is the time. http://www.evga.com/articles/00582/