You will likely get far more bang for the buck doing wall treatments in the HT than changing the speakers.

As mojo has said, the refinements you'd get will be lost in most movies that really don't rely on subtle sound stage. save the money.

Anthem: AVM60, Fosi DAC-Q5
Axiom: ADA1500, LFR1100 Actiive, QS8, EP500, M3, M3comp, M5