Building a first system

 I am planning on putting together a computer audio system and could use some help. I don't have space for a dedicated 2-channel system, but I really want to have a place to listen to my music. I want to have both speakers and the capacity to use headphones. I want to spend no more than $1,200 for the whole system. I use I-tunes with lossless files. I mostly listen to rock, blues, jazz - very little acoustic stuff.
I was looking at smaller speakers like NHT Superzeros, Aperion Intimus 4B, JohnBlue JB3, etc. I would also be willing to use a powered speaker like the Audioengine 2. I have contemplated running the music thru a dac like the V-dac or a Musicstreamer. 
Beyond that I am a little lost. What is the best way to set up the system? Is there any software out there that improves the sound of I-tunes? What kind of amp - headphone or otherwise should I consider? Are there any synergy considerations? Any thoughts? 
Thanks,
Jason