Thanks for responses. My BELS are MK IIs.I hear the MKIVs and higher are even better at driving difficult loads. My room is approx. 15 by 30 and the spkrs are situated along the short wall. I think the BELS excel at bass control, if not ultimate bass drive, and have a see thru clarity that I love which is why I am hesitant to replace them. One aspect that I've noticed with them is that the midbass seems a little subdued which is why I feel I may need a little more power. I also noticed this character when I used one BEL to drive my previous ML Aerious's. One note - there is a glass window between the spkrs which I always felt should be covered with sound absorption. Then yesterday on a whim I covered the window with a wooden board. Right away the midbass bloom improved dramatically as well as bass dynamics. Strange. I really feel though that I need to see how these spkrs sound with a very powerful amp. Thanks again.