my current build is a fx 6300, hd7850 2gb, and a ASRock 960GM/U3S3. Right now i have enough money to upgrade to CF 7850 and new mobo should i do it? will it botttleneck my cpu?
No it won't. Just do it!
NO you cannot CF at all on that mobo. since it only has one pci-e X16 slot. you will gonne need to buy a new motherboard then. and also not to forget you will need a decent powerfull psu.
your best solution would be, buying a R9-280X