If want the old sound.. there are only two amps to look for in my honest opinion.. Ampeg or Sunn.. nothing else. You will get more bang for your buck with the Sunn stuff.. I use right now a Sunn Spectrum I head.. yes it is only a 40 watt head and two (Fender) Sunn 15 cabs. The speakers are only 80 watts apiece, butt it is very effecient. I only need the amp on 3, the set up is loud enough.. You may want to look at any of the 60 watt Sunn heads, to which there are plenty of, or if want.. get a 2000S head, which is supposed to be 120 watts. In fact.. there are two of them on the Bay now for sale. The amps that everyone fights over are the old ModelT's and 300T's, and of those two, i would get the first generation Model T.
randy