The ventilation you mention is certainly sufficient so no worries there.
The P5 would certainly have plenty of power and do a great job but there’s just no getting around how much better a P10 sounds. There’s about half the output impedance driving any load, small or large, and that lowered impedance just makes anything connected sound magical. If you can, go for the P10, but if not, the P5 would make for a wonderful addition.