Hiya Gregg shocked )

The PV1 (black btw) has an integral rubber moulding that the unit sits on. The whole of the "ball" is a heavy aluminum casting, two parts bolted together with very substantial bolts. There really is no detectable vibration from the enclosure, even at full boogie - just gorgeous clean tight bass! With it being side firing it won't be pumping into your floor board cavity either...

Re the M33's - be very aware that what you'd actually be creating is a second enclosure around the first - although not completely enclosed you'll have boundaries sufficiently close to each other to give you audiable resonances, beyond the reach of the MRC. If you could line the hole in acoustic foam or egg box to break up the reflections this would help loads. Also, sloping the sides would break up standing waves.

Keep us posted! I wish I could lend you my sub but the postage would cost the earth!

Cheers, Steve