New PC Build help needed

Haven't built a PC in years but am strongly considering building one again for Crysis, Counter Strike, Company of heroes and a whole host of other games. My budget is around 800 euro without a monitor. This is the spec I've selected so far, Radeon HD 4870 1GB GDDR5, PCI-Express 2.0, DVI/HDMI/DisplayPort, Antec Sonata III Miditower, Black w/500W PSU, Intel Core 2 Quad Q6600 2.4GHz, MSI P45 NEO-F, P45, Socket-775, DDR2,
Corsair TWIN2X 6400C5DHX DDR2, 2048MB (another 2gigs), Western Digital Caviar SE16 500GB SATA2 16MB 7200RPM. All this comes to just over 850. Is this a good spec or is there anything better you'd recommend.

I'm with BLH there.. you're seriously going to struggle to expand it with that PSU and may get problems.

600 or 800W would be wise i'd think.

Ram.. yep 4 gig. I'm running three and it's fine but might as well go for four.