Look at this, this should give you an idea.
http://www.pricegrabber.com/ho...3b3cf
I get all my stuff from eBay (lowest prices almost always)
Back to which head unit: All should cost you under 150 without shipping or tax
Jensen MP3310Sony CDX-MP40
and my personal choice
Pioneer DEH-P4500MP
I owned 3 pioneer decks, I think they are the best bang for the buck, quality is very high never had any problems, and they keep their value…sold my DEH-3400 for 85 bucks (bought it for 132 more then a year ago)