Complementing Mission M cubes

Hi,

After deciding that the M cubes are what I want (and as ex demo I can afford them) I'm trying to decide on the best amp to run them through.
On the demo the local dealer used the Yamaha 457 which sounded good but the guy at the shop did say that this amp was probably at the limit of what it could do to run the cubes. I have heard from other sources that the Yamaha 757 is much better (although £150 more expensive) and that even the Denon 1906 is a better amp. I 've also read though that denon amp's are not best suited with the Mcubes!

Anyone care to make a suggestion?