Which surr/proc to go w/ Krell & Thiels?

Tom, thanks for the response. The Krell Showcase is probably a good choice since I have thier amp. I haven't played my Merlins since I got the Thiel 3.6s five years ago. They've been in storage waiting to be used for surrounds. I'm not expecting too much from them, except to give me a better sense of ambience. I currently own a Melos hybrid stereo preamp, so I haven't had a chance to listen to anything other than 2 channels. But, I'm getting closer!

I have a setup very similar to yours. I have Thiel 3.6's on the front, an MCS1 for the center. I have Krell KAV 2250/3250 amps. I use the Krell Showcase pre-pro that I got used on Audiogon for less than 3 grand. I have been extremely pleased. It works just as well for music as movies.

Highly recommended.

FWIW, I have since upgraded my amplification significantly to Theta Enterprise monoblocks on the CS3.6's, and Theta Intrepid powering the rest. I have also added a Velodyne DD-12 (great upgrade!). I still have the RSP-1066, but my next upgrade (after my Modwright tweaked Denon 5900 comes in) will probably be to either the Krell HTS 7.1 or the EAD Theatermaster 8800 Pro. I was incorrect in my prior post about the Showcase being my dealer's "highest recommendation." They really like the Showcase for the money, but sonically, the HTS 7.1 or Theta CasablancaIII woudl be their highest recommendation. Of course, they don't sell EAD.

Hummmmm...I like the krell pre/pro's, very much actually. I used to sell Thiel set up with Krell KAV250 amps and HTS processor. While the sound was very detailed and clear, some might think the trebble "walks the line" pretty thin, or close. Tastes may very. I've had clients comment that they didn't like the Treble match of Thiel 2.3's with the krell combo. But, then again the 3.6's are different speakers to my ears. It maybe a more solid match, and of course cabling will "season to taste" for optimum sound any time.
I'd give the Krell stuff a try in a heartbeat. But then I like their pre/pro's, and have gotten gorgeous sound for multi channel with them indeed.
Still, if you are woried about the top end balance, to be critical (or safe), Macintosh, Classe, Aragon, maybe CAL Probabaly EAD 8800, and Theta's top would probably "steer you safe" if you have any concerns there. All these offer superb surround processing and refinement. The AVM20 I've not heard, and am a little sceptical. But that's only because I've sold Anthem/Sonic F over the years, and just didn't hear the AVM2 sound good in any setup's I breifly heard(although that company had great products in the past, and now Paradigm owns). Although that may indeed be a great piece, I dunno. I still haven't heard any real solid reviews or demo's on that piece.
Personally, I've sold a lot of gear over the years, and have been around most all the lines. I tend to shy from the Lexicons', Bryston's, B&K's, Meridian's, etc. I think these sound more digital, warm, and or plain to my ears. Actually the Meridian is best here, but complicated, and not that special sounding if you ask me, but decent.
You'll really have to try to find out though. No other real way.
This is not a snap answer choice, as you know.