Thanks everyone for the excellent comments and discussion so far. Keep those ideas coming!
It's interesting that the VP160 discussion seems to be settling into two camps: Make it the same driver complement and cabinet dimensions as the M60 so that it matches closely in terms of bass/timbre or change the driver complement and/or the form factor into a taller, narrower cabinet to allow for smaller TV cabinets and possible wall mounting. It looks like I'll be busy with drawing up a few CAD designs and having prototypes built over the next few weeks! One thing to keep in mind is that our decision on what version to produce will be based on the outcome of our blind listening tests, even if the result is something that does not follow conventional "wisdom". That being said, we always try to take into account functional requirements and it's pretty clear that a centre channel with a smaller form factor than the VP180 might be very desirable. The porting arrangement is also something we will be taking a close look at and a sealed cabinet might be possible, the only downfall being a reduction in bass extension.

Andrew