Going with an Intel setup would be your best bet performance wise. Neither of those motherboards are compatible with the CPU you selected as they don't have the proper FSB.
This one will work: ASUS P5KPL-AM/PS
The OCZ StealthXStream is an excellent choice. Great quality PSU, But you really don't need that much power. For a bit less, you can get the OCZ StealthXStream 500W
DDR2 800 will be what you need for memory. G.Skill makes a great set: G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 800
You can't go wrong with either hard drive. I prefer Seagate drives.
Oh yea, you'll need a CPU HSF. This would be a good choice: ARCTIC COOLING Freezer 7 Pro