Mobo------- The asus one is the best choice or you could go gigabyte is also a good one and cheaper. The onboard audio, I think they got the same quality unless you buy a high end mobo. No problem with pci-e 3.0 there´s retrocompatibity for both sides.
If you receive the free ram just put it in there if not then stay with what you got, is more than enough.
Gpu------ For less than 200$ the hd 7850 is the best, maybe the 2 gb version would be better for you, the His is a solid card not just for the better cooler but for a better gpu card overall (hd 7870) go for it if you can.
Cpu----- I´d rather go piledriver than zambezi here, the fx 8320 is better overall and you can get a good Oc from it.
Well I have the $ in the bank im ready to order right at 400$ limit I believe ive done my research better than normal, staying in touch with the communities help! I appreciate all the help you guys gave and more if you have it!