How much should i sell my car system for?

im planning on selling my 2 15 soon, im upgrading to 4 12s, and im just wondering around what price i should sell them at. im going to sell my 2 ma 15s 500 rms a piece, my lanzar 4000 watt amp, putting out about 800-1000 rms brigeded, and a 3 farad capacitor.the subs i bought brand new 2 months ago, and both the amp and cap i got last week brand new as well. What do u guys think a good selling price is for this system?