Well, if you would of asked 1 month ago I could have told you where you could get a NAD c370 for $500 authorized, but they are out of stock now.
http://www.saturdayaudio.com/ does have the nad c270 for $370+shipping. For that much you could probably troll ebay or audiogon for the c160 preamp for a while. Yawaonline.com might have some nad c160 preamps left also.
Edit:
http://www.northamptonaudio.com/nad/C370.asp
Nad c370 $499 but has a blemesed carton.
FWIW, NAD c270 + c160 = better than Nad c370. I own a c370 and love it.
You may want to contact saturday audio about the c372. It was under $800 when I bought my c370.