New PC with Gigabyte MOBO GA-P35-DS3L, Comments?

I am planning to build another PC as the old one is getting tired. Of course, there are budget constrains and would like to have a good and solid performer for the money invested. The PC will be used for working with AutoCAD, gaming and general purpose applications. These are my proposed components:

MOBO: Gigabyte GA-P35-DS3L (Ver 2.0), Socket 775 (already purchased)
CPU Cooler: Nuctua NH-U12P CPU cooler (already purchased)
DDR2 Memory: Corsair XMS2 4GB(2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop
Memory Model TWIN2X4096-6400C5DHX (already purchased)
Video Card: Sapphire 100222L Radeon HD 2900PRO 512MB 256-bit GDDR3 PCI Express x16HDCP Ready CrossFire
Supported Video Card (already purchased)
Power Supply: Thermaltake Pure Power 600 watts (pending)
Monitor: LG Flat LCD 22" widescreen 1680 x 1050 (already have it)

I plan to overclock the CPU as much as possible (shooting for 3.4 or 3.6 Ghz under 45 degrees or better), but noise is an issue reason why I bought the new Noctua NH-U12P cooler. For the CPU I am debating between an Intel dual core E2200 or an Intel core 2 duo E4500, both of which are running at 2.2 Ghz except that the E2200 is a stripped-down version of the E4500 (so I read). The E2200 has an 11x multiplier same as the E4500 (so I read). At a RAM forum I was told that if using the E2200 with the mentioned setup I may be forced to lower the Corsair XMS2 from 800 to 667 or 533 to get things working. Will I be lowering my performance by doing this as the Corsair XMS2 are 800.

Appreciate comments on the entire setup and advise on two issues, which CPU would be best for the setup and proposed overclocking settings to get the most of the setup (either with the E2200 or the E4500).

Consider a 3850 instead of the 2900 pro. The 2900s tend to be loud and hot.