Get yourself a 785GT-UD3H Gigabyte mobo , it's fairly cheap and will support 1600 Mhz RAM ( provided you set the speeds and timings correct manually in the BIOS ) . Wont allow for Crossfire or anything , though ... so I'd suggest a HD 5850 or something , rather than a HD 5770 .
Or you could get a mobo that's a bit more expensive and has several full PCI-e X16 lanes ( albeit one with four of them is more than just overkill ) , and get yourself a HD 5770 and add one later on if you need it .
AMD Phenom II 965 Black Edition AM3 C2 + Scythe Mugen 2 (120mm Enermax Apollish+ 120mm Scythe Slipstream)
Gigabyte 785GT-UD3H AM3 Rev 1.0
XFX HD 5850 @ 820/1125 + Zalman VF3000A
12GB Crucial Ballistix (2x4GB Tactical 2x2GB Tracer) DDR3 1600 Mhz 8-8-8-24
Antec 1200 case
Samsung F3 1TB 7200 RPM
LaCie 1TB 7200 RPM ( Actually a Hitachi Deskstar )
Windows 7 64bit
42" LG 42LV4500 1920x1080
Microlab Solo 7C speakers