If you want more power you could always buy some of the components off of ebay, as there are lots of great deals you can get. If you want everything brand new, then I would go for the Techreport build that WR2 suggested. If you end up going for the techreport build you should get an aftermarket heatsink so you can overclock the E5200. I don't know about the 380w PSU that comes with that antec case though, it may be a little underpowered for gaming.
Also agree with WR2 on the Quad and definitely get 4GB RAM if you get any form of Vista. I have seen it go for $30 on newegg so theres no excuse for getting 2GB for $24 unless you're on XP.