Arc's are awesome amps, they are the makers of Zapco's so expect some audiophile results. I got my 4050xxk for about $300 new w/ birthsheet and all. The 4150xxk you should be able to get around $400-$500, depends on whats included, used/new, warranty etc.. Just be carefull if you goto Arc's website it states that warranty will have NO effect if purchased anywhere else but from them or an Arc authorized dealer.