As Prototype18 says:
I'd recommend a build based on this:
1) CPU-> i5-3570K
2) motherboard-> 1155/Z77 (Asrock, Asus, Gigabyte. ATX, not uATX)
3) 8GB DDR3 1600MHz (possibly 2133MHz)
* Some games can take advantage of 2133MHz DDR3. However, NO GAME can benefit from more than 8GB. You are better off spending the money on 8GB of 2133MHz rather than 16GB of 1600MHz.
I can't recommend an AUDIO card without more information as to its use, but you should be getting one.
I can say I love my audio card:
Auzentech X-Fi Forte
I have these speakers:
M-Audio AV40 (stereo) which some audio pros have used