I have the 2.4's in a combined HT and stereo. First of all, you do need an amp that can really drive them. Makes all the difference in the world. With that said, I woukdn't even look at a AVR... Go separates with an amp that can double it output into 4ohm. Also, get some good cables, Cardas match the Thiels well IMHO.
I recently used a Krell KAV250a and that does sound good, just replaced it with a Mark Levinson 334 and that sounds even better.
What are you planning to use for center, surround etc?