Dealers make me laugh sometimes,they always have some hidden agenda ($$$)the dealer over sold you on amps and under sold you on subs IMO,
you should have bought better subs..and 12s if you have room.
I have installed Mclass subs before they are entry level subs without question-
I used to get the for like 70 bucks each,$10 more than the PR's which IMO they are just fancier PR's.
Did you try tuning the system more crank the gain up a little,move the Xover settings higher etc?
Diamond D3s is one alternitive you can try,2 10's u wont have a problem using all that amps power and youll have
some nice headroom and it shouldent cost more money since the subs are priced closley to M's.
But she wont like them either it ,sounds like she has expensive taste and 2 D6s will walk all over all the above mentioned anyways so maybe
Get the dealer to swap them out if possible cause a D6 will kick *** in a small enclosure
have the dealer wire them up as 2 D4s in parrallel so youll get that amp to a 1ohm final load
and feed the D6s 550w each
then watch her be all smiles