Need Expert Advice.....

Hi guys,
I am about to build a new pc and need your expert advice.
I will be mainly using this for playing games. I also want it to be future proof so any advice regarding that will also be appreciated.
Feel free to modify the components that i have selected. all prices are in UK pound sterling.

Antec Nine Hundred Gaming case Black full tower £65

Lite-on LH-20A1S-10C SATA Beige 20x DL DVD +/-R/RW RAM oem £16

OCZ 600SXS StealthXStream 600W PSU £47

Gigabyte motherboard GA-P35C-DS3R Intel P35 Express LGA775 £72

Intel CPU Core 2 Quad Pro Q6600 95W Energy Efficient 2.4GHz SLACR G0 Stepping £163

500GB Seagate Barracuda SATA II 300 7200rpm 32MB cache Hard Drive oem £69

Corsair 2048MB TwinX XMS2 6400 C4 DDR2 4-4-4-12 800Mhz Memory Kit (2 x 1024MB) £40

Gigabyte GF 8800GT SLI 512MB DDR3, PCI-E, DVI, HDTV Out, Retail £164

Acer 19" TFT LCD monitor AL1916WASD widescreen DVI 5ms Silver £121 brightness 300 cd/m2 contrast 700:1

i have a few questions now.
will the psu be enough if i add a second GT card in the future or even upgrade my cpu or add another hd?

Do i need a PC7400 memory module to match the cpu speed or PC6400 would do?

should i wait to get a OC version of GT card cause they are currently out of stock.

Does brand name really counts cause i can get another monitor from different manufacuturer for a lot less price.
Hannspree 19" TFT Monitor New York Widescreen 16:10 5ms With DVI 700:1 brightness 300 cd/m2 £105

Any suggestions would be Highly appreciated.

Thanks.

Strictly aesthetic but why are you getting a beige DVD writer with a black case? Otherwise nice system