That's the beauty of these amps, they have Combos, Heads and Rack stuff. for instance if you're on a budget and like rack gear, you could but the Empty preamp chassis for $400-$500, and buy the Preamp modules 1 at a time. Then run the Preamp into the Effects loop on your Combo Amp or into a dedicated power amp until you get the cash for a Head or Combo. When you get the cash, sell the preamp chassis for a minimal loss and keep all the preamps you've bought.