RAM RAM RAM !!!!!!!!!!!!!!!!!!!!!!

im planning to buy one psu and ram, as per psu matter ive reently bought xfx hd 5770 1gb gddr5 card, is there any psu's has the compatability of ATI crossfireX like the nvidia sli having and also everybody knows ati 5770 consumes very less power, so what im thinking is whether i hav to go with 500 or 450 watts PSU, and also corsair or coolermaster (make sure the products are available in INDIA & also prices).
and coming to ram side which ram will be better for ddr2 800MHz corsair, kingston, transcend with less latency timings..... and also which will be good
1. unbuffered, ECC
2. buffered, non-ECC
3. Registered, ECC
4. Registered, non-ECC, actually i hav read one article in tomshardware only regarding ram selection that buffered rams are used for servers, for normal desktops unbuffered, ECC will be better as im a hardcore gamer i need fast processing RAM only plz suggest me for above mentioned quieries THNK u.
my mobo already installed with transcend 2GB DDR2 800MHz.
CPU : AMD ATHLON X2 6000+ 3.0GHz WINDSOR
MOBO : ASUS M2N-SLI
RAM : TRANSCEND 1x2GB DDR2 800MHZ
VIDEO CARD : XFX RADEON HD 5770 1GB GDDR3
HDD : 1x80GB SATA, 1x256GB IDE
OLD PSU : ZEBRONICS 450Watts SATA +