You should be able to do 3gigs on it without any problems.
But personally I prefer to use 2GB or 4GB, I don't like odd numbers
Nah, it's just my superstitious
Well, seriously I don't see much benefit of 3GB over 2GB on gaming (at least up to current titles). And on the other hand the pricing of 2x512MB is not much differ to 2x1GB. So why not 4GB? Or get 2x2GB, so you can use the other 2 empty slot later on. I regret myself of getting 2x1GB instead of 2x2GB when I bought mine.