Considering the typo in the OP I will guess the '^' should be a '6' and he has M60s as fronts and is wondering if the M50s will fit in anywhere. As was mentioned rear surrounds would work if you have the room and an avr capable of 7.1 or is there any other room you would want some sound in?

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70