Matching Amps and Preamps--any Combo?

Let's say that you want to experiment with separates. Can you buy ANY preamp and match it with ANY amp? What should you look out for?
I'd start from ANY room first.
No way. Synergy makes or breaks any system, even the $100k ones. Room too for sure. For the components, you have to watch for impedance matching, capacitance matching, level matching, and tonal characteristics, all of which are only obtained by trial and error, or simply by getting both preamp and amp of the same brand. I favor the latter since it is a zillion times easier. Good luck.
Never look at the specs and for sure you will wind up doing it by trial and error. Get on target first with objective parameters, then you can start with the audiophile approved "search for synergy". The last part is the crux of subjective audiophilia: the match you make may or may not have widespread audiophile approval (ask three audiophiles about anything and you will get five different opinions) that's ok so long as the sound pleases you.
what you need to do is listen to all combinations of amps preamps cd player and speakers. matching the same amp and preamp does not mean it will sound great.
If your amp can except a Passive get one .

There are things to consider.Impedance Matching and Sensitivity .Cables need to be low in Impedance also.

These are equated into Gain issues.

The FT Audio Passive preamp gets around some of this by using a special circuit named the Xcoupler.

Other alternatives are made by Creek and Placette.I would shy away from CI Audio.

Good luck!