Tube Preamp/solid pwr amp or solid pre/ tube pwr

While as a general rule I would advocate for the ss preamp/tube power amp combination, in this case I think you may be asking the wrong question. The overriding question that should be asked, IMO, is what kind of power amplification, and what particular power amplifiers, would be the best match for the particular speaker.

I couldn't find impedance curves for the Nautilus 802. But if they are anything like the curves of the 802D or the Nautilus 801, the sound that is produced will vary dramatically depending on the output impedance and the drive capability of the particular power amplifier. With those impedance curves, among other differences tube amplifiers will give greater emphasis to the upper mid-range and lower treble, while solid state amplifiers will give greater emphasis to the mid-bass region. In addition, many amplifiers, especially some tube amplifiers, will have difficulty driving the speaker adequately in the deep bass region, due to the combination of low impedance and highly capacitive phase angles that is reached at some frequencies in that region.

So my feeling is that the initial question that should be asked and researched is what power amplifiers have users of the particular speaker found to be best.

Regards,
-- Al

04-17-12: Bondmanp
I have no idea what the impedance matching issue is for SS preamps with tube power amps.

Usually none. Solid state preamps will usually have relatively low output impedance, and tube power amps will usually have relatively high input impedance, which is an ideal combination. The higher output impedance of many (but not all) tube preamps, and the rise in that output impedance that will often occur at deep bass frequencies as a result of the output coupling capacitor they commonly use, combined with the relatively low input impedance of many solid state power amps, will cause the deep bass rolloff you experienced, and/or other frequency response anomalies.

Regards,
-- Al