Looks good. I'm a fan of OCZ Platinum, but to each his own. Phenom II 720s are all the rage right now, but you're not shooting yourself in the foot (to hard) by getting a C2D. A triple-core will run any dual-theraded game more than well enough, and will handle background chores more easily, and will give you a leg-up in quad-threded games, but again, to each his own.
so I've changed the memory to OCZ 4GB PC2-6400 Platinum XTC Edition Dual Channel DDR2 Kit (2 x 2GB) and the PSU to PC Power and Cooling Silencer 750 Quad Power Supply, Crossfire Edition which will save me about $30.
As for the processor which do you think is better, AMD Phenom™ II X4 810 Quad-Core 2.6GHz w/ 6MB Cache (Retail Box, Socket AM3) or AMD Phenom™ II X3 720 Triple-Core Black Edition 2.8GHz w/ 7.5MB Cache (Retail Box, Socket AM3)?