gakman, the RM-200 Mk.2 (make sure you get the Mk.2 version) is a great choice. It has a bipolar input stage and tube driver and output stages, using KT88 or 6550 tubes. It does not have the old-fashioned tube sound (soft bass, excess warmth, somewhat rolled-off highs), instead sounding very fast and clear, with tight bass and an extended high end. If your speakers and room (and musical material) can get away with 35wpc, the RM-10 Mk.2 would be nice too. It has a tube input stage and uses EL84 output tubes. The RM-10 is a favorite with owners of Quad 57’s, a notoriously amplifier-finicky loudspeaker.
The RM-200 Mk.2 has an input impedance of 60kHz, balanced only. Roger Modjeski says the performance and sound of the amp is not compromised when fed by a single-ended pre-amp, unlike some balanced circuit power amps. I got mine in Mint condition for $2500, but they usually go for around $3000. There is also the "T" version, with output transformers hand wound by Roger personally. That adds around $500 to the price used, but they are rarely seen.
As for pre-amps, check out the EAR-Yoshino 912 (with meters and rack mount handles, for studio use) and similar 868 (a less-feature version of the same basic circuit). Designer Tim deParavicini does a lot of work in the Pro sector (Pink Floyd Studio in England, the electronics for Kavi Alexander’s incredible Water Lily tape recorder, maybe the best analog machine in the world), and the 912 and 868 feature transformer-coupled balanced/XLR outputs (two pair on the 868, plus another two pair unbalanced/RCA) designed to drive the studio-standard 600 ohm impedance. They don’t care WHAT the power amp’s input impedance is! They also sound great---read Art Dudley’s 912 review in Stereophile a coupla years back if interested. Art wanted it bad, but already has a real nice Shindo, and the 912 ain’t cheap.