Recommendations for PC -- for modest system --

Looking for recommendations for PC for a modest AV system -- I know all things audio are personal preference - but still want feedback on experiences with PCs under the the <$400ish mark - 

My meager system:

Marantz 7705
ATI 7ch x 200 amp
B&W CDM9NT x4 plus matching center

Budget - is low compared to many here - but still looking for some solid guidance - <$400 for each PC for amp and AVP. If I can spend less - that is ideal - Not looking to squeeze every last bit of sweetness from my AV system - just want something that is a balance between - far better than stock PCs -- and improves system overall - on the exponential curve of price vs performance.

Considering the following: 

Morrow
Audioquest - one primary reason I am considering AQ - I can purchase at 45% msrp...
Nordost
Raven
Madscientist - unfamiliar but seem a few here have exp with them... 
Cullen
DIY?  -- Can I approach equal or better quality - for less if I DIY with the likes of with neo or dh cable or other with WG or other connectors... Is it worth the effort to DIY at budget I have set? 
Synergistic Research - considering - but I see none in the <$500 range... 

Thanks in advance.