Certainly having full speakers all around for DVDA or SACD is a common practise, but not two towers as centres. I'm not sure using the M60 togethor as a centre would be the best use of them. For DVDA/SACD I think they'd be better used for surrounds leaving the V150 as the centre, and the Q's ( if you have them ) as rear surrounds. For Movies I'd switch the side and rear surrounds, but either way I think this would be pretty much major over kill and likely you could accomplish a better bang for the buck by spending the money on another part of the system.
But I guess it really depends on what you're trying to accomplish by doing this...? As Haoleb suggested I'd think you would only need one tower in the centre. If you're using two consider the resultant ohmage (1/r + 1/r=)...
Cheers
