These speakers are capable of some huge SPL even in the largest rooms. Playing them too loud in a small room will sound bad. Regardless of the space, playing them @ high SPL with insufficent power will lead to amp clipping and related distortion.
As with most things, finding the correct balance is the key. If you have a big room and like to listen at concert or movie reference levels, then you will need a adequate power.
If you like more moderate volume and have a smaller space, most any AVR will do but you will not be taking advantage of what the JTR's do best.
Opinions are not facts.