First of all wait for a couple of weeks so that bulldozer chips come out, they should be much better than the previous generation.
You can get many memory kits from gskill for example that have: 2x4GB 1.5V CAS9 1600Mhz specs.
Which you should have. Gskill ripjawsX 2x4GB 1.5V CAS9 1600Mhz
Mobo you want to make sure it has an AM3+ socket. Asrock 870 Extreme 3 R2.0
for example fits the bill $92
XFX has a good set of PSU's. You should be fine with about 550-650W PSU.XFX Core Pro650W
$89.99 ( before $30 MIR )
GPU: If you can fit it into your budget a 6850 can be had for $135 after rebates. Nice amount of additional performance over 6770 or 5770.