Tube Preamp with Solid State Amp?

I have used a tube preamp (Audio Research Reference 3) with a solid state amp (Audio Research 100.2) with medium efficiency speakers (89-90 dB) with great results. As stated above, it gives you the best of both worlds.  You get the 3D soundstage with tubes and bass control with solid state. For your highly efficient Cornwall IVs however, I would suggest a SET tube amp (e.g., Coincident Dynamo) or a lower wattage tube integrated such as Quicksilver, Leben CSX300 (15 wpc with EL84 tubes) or perhaps Linear Tube Audio 10 watt ZOTL.  I have a Coincident Dynamo 34 SE mark ii amp (8 wpc) with my Klipsch Heresy IIIs, which offers very good bass control for a SET/SEP amp with EL34 tubes, excellent 3D soundstage, but more of a clear detailed solid state like treble (rather than vintage buttery warm tube sound) with rolled off smooth highs. Just one more opinion. Good luck!

If you haven’t already, you should check out the Klipsch forum. I think that many who purchase high efficiency speakers do so because they highly value dynamics in the musical presentation, and they want to use them with SET amps. Klipsch and tubes are a magical combination. I remember visiting an audio store in the 70s and being blown away listening to a Sheffield Track record on a system with McIntosh tube gear and Klipschorns.  Solid state amps with Klipsch speakers can be quite good, especially with a warmer presentation offered by the likes of NAD or Parasound that takes some of the edge off an otherwise strident fatiguing treble. But most Klipsch Heritage line 2 channel systems I am quite certain are being driven by a tube amp.  If you decide to experiment with a tube preamp, I would suggest a used Audio Research preamp with a more euphoric sound rather than something like C-J with coloration, given that your Parasound amp is already on the warm side. I think you are wise however to try out a low wattage tube amp that can be a relatively low cost experiment (e.g., Decware, Coincident, Bottlehead if you have DIY leanings). 

Euphonic. Argh

Autocorrect euphoric ended up euphoric. 
And one more thing for jji666 (?Lucifer), I wasn’t sharing my gear and difficult audiophile journey to brandish my wares, but just offer my experience. So speak for yourself. 

Haven’t heard from the OP for awhile. Fairly safe to presume that the Parasound gear predated the 4th iteration of the Cornwall in your system. I am by no means knocking Parasound, as I think they manufacture well-engineered solid state gear for a fair price. While I think a tube preamp with solid state is a great combination for most systems, I am not sure it is for the Cornwall. Dick Olsher famously remarked that “the first watt is the most important watt”. You will likely listen to no more than 1 watt with that speaker in a small to medium sized room, so it better be a good one, or the other 249 in the case of the A21 are a waste.  Do yourself a favor and either use the A21 for a second system (driving an inexpensive inefficient bookshelf speaker perhaps), or sell/trade it. Get yourself a flea watt single ended DHT (2A3/300B/845) amp and find out what Olsher meant and what you’re missing.