Jools, That listening level is probably what I use  The MB2's are large puppies. Im having a demo of some IB2's next friday with bryston amps. These have the same upper drivers, but with a smaller cabinet and bass. I'll be comparing them to atc 50's.

I am expecting the IB2's to have a lower bass extension, but most probably it will be more 'one note' bass, due to the design. I also expect the ATC's to have more presence at lower volumes. Overall I don't think the PMC's will sound as quite as good as the active ATC's with a valve pre, but we'll see. Although I could be talking kack.