asuming it for gaming and you want it to last a year/year and a half i would go with this...
GPU:im not sure if u mean u want 2 9600gt's sli...if so the galaxy brand has good cooling, can oc well and looks very nice (i have one and will be getting another one soon)
HDD:if you don't plan to use raid 0 get one hdd :seagate 7200.11 500gig 32mb cache would be good.
Ram: 2 gb crucial ballistix or 2gb g.skill (800mhz)
OS: id say windows vista home premium 64bit.
Optical drives: blu ray is not neccisary unless u are watching blu ray movies on ur comp or burning them... just pick up a sata dvd writer,,,the only reason to get more then one optical drive is for u can have ur fav games in them for u don't have to switch,, or for u can burn a dvd/cd directly.
PSU: for that system a 620hx or pc power and cooling 610w would be perfect.
CPU: If you don't want to spen alot of doe the q6600 is still the best bang for the buck
CPU heatsink: if you want to oc go with a true,tuniq tower,, if you don't want to oc u can stick with the retail cooling or get a artic cooling freezer 7.
SC: some say a sound card does increase performance and some say it doesn't...its really up to u.
MOBO: depending on how much u want to spend on it if you want it to be upgradeable for a good while i would go with a 780i, if ur going to upgrade to mobo in a year then id say a 680i would be fine.