I'm considering adding one of these preamps to my dedicated 2 channel system. I primarily use vintage tube amps like Fisher SA-100, Pilot SA-232, and my clone Acrosound mono amps (yes, I love vintage EL84 amps). Are these solid state preamps compatible with my tube amps. I know they will work, but is there some ohm specification between SS and tube that can cause a mismatch? C500 is available in tube or solid state, but the 100 and 200 are solid state only. I know I've read about this potential mismatch, but I don't understand it. I also don't know what will make my tube amps sound their best. My current pre is an MX110z, which I plan to more to a different system.