I have a similar problem. As my SWR Redhead fadet out unreparable, I now use the cab of the combo. My tech managed to install a poti that reduces the power of the tweeter, which is originally controled by a knob on the back of the Redhead.
First I tryed out a SWR Redface - nearly he same sound as the Redhead! No wonder, as the Redface is nearly the same amp as the Redhead...
Second Try: A Markbass LM II. This one does not fit at all to the cab - in my opinion. I couldn't dial in any sound, that suited me. The ported cab goes too low, I couldn't dial in the mid shape I wanted. Astonishing, because I like the LM II a lot if played over a 2x12 Workinmans cab.
Third try: A Peavey T-Max. This one is beautiful with that cab! As the ported cab goes down to the deep end and up to the highs a lot, it misses nice mid frequencies. This is, what the T-Max produces: Nice, growling mids. So this was the best combination.
As the sound of the Peavey comes quite near to what they call "SVT-Pro - Sound" (solid state amps, you know it...) I think, that it will sound fine with a SVT 3 Pro or SVT 7 Pro. I couldn't test it by myselfe, because I just got me today a SVP-Pro preamp. I already have a suitable poweramp, so I will give it a try when having the SVP at home.
I think, that any amp with stronger midrange is suitable to a SWR poted cab. As well - I think that any SWR - amp suits to it...