Never heard of OCS.
Also Crosshair isn't a brand,I think you meant Corsair which is a reputable brand.
8GB is more than enough for games/apps so unless you're going to do "extremely" heavy video editing,you'll be fine with 8GB
if i choose to have 8 gb , do i need to have 2 stics of 4 gb each for duel channel or 1 stick of 8 gb will be ok to work as duel channel? and i c some different mem 's of same specification but different prices