I can't suggest anything to pair it with to get the best synergy, but I can tell you from what I'm reading the amplifiers input impedance should be 10X that of the Preamplifiers output impedance. This is just a general rule of thumb, and my guess is this won't be much of a problem with most equipment. I have somewhat the same problem and have a nice preamp that was used in my headphone system, and I would like to get a power amp with it. I'm having the same issue of what to match it with since the manufacturer doesn't make power amps. I may purchase the amplifier from a company that has a generous return policy.
Power Amp Pairing
I have a Pioneer SPEC 4 amp and SPEC 1 pre-amp. The power blew on the SPEC 4 in January and the repair is complete. There is, however, still some slight distortion coming through the right channel (I've checked everything...different speakers, different speaker wire, etc.). With the length of time it took to get it repaired, I'd prefer not to take it back for further repair. So, the question is: can i purchase a new/used power amp of ANY brand that will pair nicely with the SPEC 4? If so, what i do i need to consider or be careful about?