Better Amp for Cornwall IV's...

Try a passive preamp with your Parasound amplifier. Do you have a source with a variable output ( bypassing the preamp )? Because of the very high sensitivity of the CW4s, you do not need the additional gain of a preamp, and a layer of noise and distortion will be eliminated ( IME ).

You really need to look at the measured impedance curve.I tried to find these measurements but had no luck.If the impedance does not dip below around 6 ohms then an amplifier with a highish output impedance [typically tube amps and not SS /class D amps would be the best choice].It would seem pretty silly to make such a high sensitivity speakers not to suit those types of amps but it is possible that is what Klipsch have done.If the speakers sound a bit weak or dry in the bass that is probably because the amplifier being used has too low output impedance.Which is typical of SS amplifiers including most class A ones .Adding more power will not fix this because the bass response is overdamped by using that type of amp.
If you do not want to use a tube amp then the best choice would be a Bakoon SS amp which operate electrically more like a tube/SET amp and which are current drive and have high output impedance.[Just about all SS amps are voltage drive/low output impedance]The Bakoons also sound superb and are a compelling example of why current drive /zero negative feedback/high output impedance amps sound best [if your speakers suit them and most mainstream speakers don’t].

Yes the Klipsch site gives you absolutely no help in terms of some pertinent specifications. I think they something to the effect that some or all of their speakers are 8 ohm compatible or some such nonsense. I pretty certain that the curve of most Klipsch speakers are not ideal for tubes but the high efficiency will cure some of the other ills. 

I was fortunate enough to spend a few hours listening to Tri Mai's system a few weeks back. Tri is the owner of Tri-planar tonearms and I had one of his arms put on my Merrill-Williams table. Tri has a very impressive horn system that I think would make most horn enthusiasts drool. He uses modified Classic Audio speakers with Atma-sphere Novacrons (OTL) and a MP1 preamp. For what horn lovers like I havent heard many systems that deliver in these areas better than this system. 

I assure anyone who cares that the Cornwall IV can achieve extremely loud levels with only 20 watts of tube power in a relatively large room. I do it all the time.

Six months of listening to the cornwall iv’s paired with a mc275 MK VI and a c2600 preamp has definitely changed my attitude towards tubes.