Never buy more than 4 GB of RAM.
Retail stores are just ripping you off with 6 GB of RAM, it's usually on a 32 bit OS that can't even utilize more than 3.3 GB, and even if it could, even with heavy gaming, you won't be utilizing more than 3 GB at any time.
Get 4 GB and you'll be set for quite a while. You'll still be good with 2 GB if you choose that though.
And don't get a GTX260 or 280, unless you see a really good deal, the Radeon 4870s are cheaper and perform just as well. Lower than that, an 8800 or 9800 would do great though.
LEFT4DEAD411.COM
Bet with disolitude: Left4Dead will have a higher Metacritic rating than Project Origin, 3 months after the second game's release. (hasn't been 3 months but it looks like I won :-p )