Congrats on being a Beethoven owner! That's one of the finest speaker systems ever designed. I take it you recently acqured them?
The subs are especially fond of plenty of current capability and a high damping factor (in other words, plenty of slam). Amps that come to mind are Pass X series, Clayton, Electron Kinetics (used of course), and Boulder. I'm sure there are plenty of others. Disclaimer - I sell Clayton.
I sell a couple of brands of dipole speakers - one dynamic and one electrostatic - and I've owned dynamic dipoles for most of the past dozen years or so, including a couple of my own design. I almost bought a pair of Beethovens a few years ago.
Choice of amp to drive the subs makes more of a difference with the Beethovens than with conventional speakers because those dipole subs are so incredibly articulate, and their one minor weakness is they do tend to lack a little slam if the amp doesn't excel in that area.
The actual power requirements aren't terribly high. I was in Siegfried's home listening to his Beethovens in January, and he was using a couple of homemade 100 watt amplifiers on the subs, as I recall, and the dynamics were stunning. I'd never before heard such pitch definition at such high bass levels. So anyway I'd say err on the side of quality rather than quantity.
Best of luck to you!
Duke
