Yes heavy bass played loud taxes amplifier power.
The "45 watt tube amps" are being used to play normal music at normal volumes. period.
The 600 watt amps are for dudes with small dicks...
As compensation. (i guess)
The Parsound seems to be in the middle, or 'reasonable'
Elizabeth, like I told you on our date at the beach, it was just "shrinkage"!
But seriously, I've measured 105db peaks at my listening seat on acoustic jazz played at realistic levels. I've also measured about a 5-6db loss between my listening seat and 1 meter from the speaker. Assuming a 4 ohm, 86db/2.83v/1-meter speaker is 2w at 86db, then 110db output at 1 meter would take 512w for a momentary peak. Some rooms aren't as lossy as mine and don't suffer much loudness difference at all between one meter and the listening seat, but some will suffer more. 105db peaks are, admittedly, very loud, and a lot of speakers can't comfortably get that loud anyway. Nonetheless, in a large room with a 4 ohm, 86db sensitivity speaker, 600w/ch is not entirely compensating for something. Of course, for Maggie owners this is an entirely academic conversation, because even a 20.1 doesn't sound very good at live listening levels. Or if your listening levels peak at, say, 97db at one meter, then a 45w amp will indeed work just fine. But a trumpet is louder on peaks than 97db at one meter, no less a rim shot on a snare drum.
Most of time I'm listening at 85db or less (mostly less) volume levels at my listening seat, and the highest peaks are in the 95-100db range, depending on the material. 45w/ch would be quite marginal, even under normal circumstances.