I have been through a fairly similar experience, so perhaps I can be of some help. First off, I tend to agree that the 3.6's (and Thiels in general) are not "bright" or overly forward in and of themselves. However, they will certainly reveal every flaw (and gem!) in your associated equipment, so you are smart to look for a good pre/pro combination. I started off with a Rotel RSP-1066 pre/pro (more on that later) combined with Adcom amps (a GFA-555II in bridged mono on each 3.6). The more I read, the more I decided that it wasn't a good idea to be using the Adcoms bridged into such a difficult load (whihc would sometimes present a 1 ohm load to them in bridged mono). Plus, it's always nice to have an excuse to upgrade, so I listened to numerous amps with my 3.6's. You may have seen my thread on the topic. If not, check out "Best affordable amp for Thiel CS3.6."
None of the amps that you have listed made my short list, although the MF amps would probably work well, and the Rotel is capable, though not ideal, with the 3.6's. It is my understanding that the 3.6's are some of the most difficult speakers to drive, and with a 4 ohm nominal load, they spend a lot of their time at 2 ohm. Because of this, I was recommended to stick with the 7B's or 14B if I went the Bryston route. With regard to Krells, I was told by many people (including the folks at Thiel) that the KAV series would not be a good match, but that the FPB series is a very good match. FWIW, I have been very pleased with all of the Krell preamps that I have heard, and this is an area where I predict that Krell will have much success.
My choice of amp was Theta, and I really think that you can't go wrong with ANY Theta amp. I am picking up a pair of Enterprises to power my 3.6's (which are well out of your price range), but I also picked up an Intrepid 5-channel and have been using it to power my 3.6's until I get the Enterprises. Even though it is only 100wpc and it's a 5-channel amp, it drives the Thiels stunningly well. In fact, at $460/channel ($2,300 for the amp, demo), it sounded equally as good with my system as the tricked out Edge NL-10 ($6,500/channel) which I auditioned in my home. Of course, the remainder of my system is not up to such a level as to hear every nuance, but still, you'd expect to hear some difference. Certainly, the Theta and Edge could both be heard to be a noticeable improvement over the Adcom (which all in all is still not bad for the money). Certainly, the Intrepid is in your price range, although you may not need 5 channels. A used 2-channel Dreadnaught (or Dread II) might be within your price range, and would be a killer match. I debated for quite a while between a 2-channel Dreadnaught II and two Enterprises.
Back to preamps. I am not sure if you are after a multi-channel or 2-channel preamp, but I have found Rotel to be pretty darn good at their price point in both regards. However, after I purchased my 1066, Rotel came out with the RSP-1068, which in addition to better DACs (same as the 1098, I hear), offers an analog bypass in 2-channel mode, which is nice. So, I think that I am going to upgrade to the 1068. Most of my preamp shopping has been geared at a multichannel pre/pro that also allows for a great 2-channel experience, though. The Krell Showcase is pretty good, but their HTS 7.1 currently tops my wish list. Again, though, Rotel is very good for the money. However, if you are sticking with 2-channel, though, I have heard that Thiels work well with a tube pre and SS power, so I'd at least audition some tube preamps. Their seem to be scads of great 2-channel preamps here for sale on Audiogon, so I think that you can pick up something nice.
Hope this helps, Tom.
