DE, the M2s should be excellent for your use when combined with a sub. The info you received on the PB-10 is a bit misleading; it does in fact have a single line level input and no high level inputs for bass(not just LFE)but that's certainly usable with a receiver which has a line-level sub output. Your 3480(somewhat unusually for a stereo receiver)has a sub output and would be usable with the PB-10 if that attracts you. The Velodyne subs mentioned wouldn't have the extension of the PB-10, but are of course much lower in price.
As far as power, it's unlikely that more than 20-25 watts will be used, even on brief peaks, so don't worry about it.
