I've had both very good and not so good experiences with a tube pre amp and a solid state power amp. The main thing to watch out for is that many tube pre amps have a rather high output impedance and some solid state power amps have a low input impedance. In my not-so-good case, the mid-range was actually unbelievably good, but the top to bottom balance was off. Since the Classe's appear to have about a 75k ohm input impedance, you should be safe.
