11-11-08: FreemandRedone with different drivers and/or crossover? If so, it might be hard to know what the specs and impedance curve are now. The original 104/2 specs were - 92dB/W/m at 4 ohms, 55Hz to 20kHz (+-2dB).
I have some Highly modded redone Kef ref 104/2
Since you are a fan of midrange, tube integrated seems a natural choice and the 92dB efficiency is a fairly easy load provided there aren't some big dips below 4 ohms. And the 55Hz lower limit should save a low-priced tube amp from having to produce the hardest frequencies.
Anyway, in your price range, you might want to look for a Jolida tube integrated in the 40-60wpc range like the JD-302B(50wpc) using EL34 tubes that's for sale here at $595. EL34's are pretty meaty output tubes, soundwise and do a good midrange.