Thanks for the info biswa002.
I'm not a Yamaha bloke, so I don't know... does YPAO calibrate the system to film (SMPTE/Dolby/THX) reference level? If so, -35dBMV (master volume) is not a particularly loud level; equating to theoretical program peaks at the main listening seat of about 70dBSPL for each channel. At 10ft (or about 3m) there'll be about 5dB attenuation with distance in a typical domestic room, so the speakers will need to be producing 75dBSPL peak at 1m distance. Your front speakers have sensitivities around 90dB/1W/1m, so on average will need less than 0.05W to produce a 75dBSPL peak.
What's the loudest you'd ever listen at? If you crank it up to -15dBMV, or subjectively louder by a factor of four (in the mid frequencies), the power required to produce theoretical peaks of about 95dBSPL (@ 1m) is still only 3W*; with average program levels in fractions of watts. Having said that, if you've bumped up your channel trims up, the power requirements will increase accordingly. If they're +3dB those power figures double; if it's +5dB the power figures roughly triple. Assuming I've interpreted your Yamaha's volume level correctly, at -15dBMV you're probably not calling for more than bursts of 10W maximum per front channel. Obviously, this power output is well within the capabilities of the Yamaha.
In terms of your speakers, they don't "know" if those 10W bursts are coming from a 30WPC amp or a 300WPC amp. If it's within the linear operating range of the amp it makes no real difference. The difference in sound that you
experience (improved detail and clarity) can be due to several of factors, including listening at a slightly louder volume along with various subconscious biases that are inherent and unavoidable when having a sighted, casual "listening session" with a piece of audio equipment.
If you have $3K burning a hole in your pocket and your goal is a real, measurable improvement in sound quality, amps would be the last place I'd look. The real gold is in speakers and doing what you reasonably can to optimise their response in your room. A perfectly matched front three speakers would be priority one, either all Studios or all B&W's. Of course, you might just love the idea of a big beast of an amp ticking over at the front of your room, and there's nothing wrong with that at all.
The reason I asked about your subs is because subs
significantly reduce the power demands on the AVR by handling the power hungry lower frequencies. (Each octave you drop requires four times the displacement to maintain the same SPL.) In this case though, as the power demands are relatively low in comparison to the capability of the Yamaha's amps, the sub's contribution is quite academic.
* Use the "dB Power Ratio Calculator" at Crown Audio's site. (Sorry, the forum still thinks I could be a 'bot, so I can't post links yet.)