I am planning to buy a dedicated amp for my RtiA9's (fronts).

I am planning to buy a dedicated amp for my RtiA9's (fronts). Please recommend if Emotiva XPA (2 channel) would be sufficient (300 W pc @ 8 ohms) or would I require a more expensive Emotiva XPR (550 W pc @ 8 ohms). Please recommend, also if members have an Emotiva XPA used to drive Polk Rti A9's. does the amp drive the speakers well enough or seem short of power.
I am currently driving my fronts with Yamaha Aventage 3070 (Fronts bi-amped and 7 other surround channels), the front channels seem grossly underpowered.

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