Hi BuddTX,
Yep, more drivers in the M80 do let it play at incredibly high sound levels in big rooms. But never generalize about personal preferences in volume levels. Big rooms with vaulted ceilings suck up hundreds of watts. During some listening tests of Axiom's new EP600 DSP subwoofer, a colleague of mine cranked up five 250-watt per channel monoblocs and the two power amps driving the M80s, each with 250 watts, shut down because they were clipping. I had to leave the room it was so loud, but my colleague loved it (until the amps shut down!).
Don't even think about putting M22ti's into a big room. Tonally, they are very close to the M80s and M60s in the mids and highs, but like any compact speaker they have limits in output level. In an average room (about 20 x 14 x 8), the M22ti's will play as loud as I ever want (with a sub). That translates to listening to classical, jazz, some rock, opera etc. at about 85 dB SPL (C weighting), sitting about 10 feet back, which subjectively is termed "quite loud," with occasional dynamic peaks to 98 dB SPL (very loud).
If I switch to the M80s, and want louder for test purposes, the M80s will do it and still sound very clean to way past 100 dB SPL, even in big rooms.
In stereo only, the larger enclosure of the M80s does result in slightly deeper bass and more output than the M60s. If you are running a sub with them, these differences become very small, only audible with immediate A/B comparisons, and even then I find my preferences change with program material.
Do not assume your Pioneer will drive a 4-ohm load at full output. If it has a 4-ohm switch or a menu setting for 4-ohms, it likely won't, THX certification notwithstanding. My recommendation of Denon, H/K and NAD is based on customer (and personal) experience with the M80s and these brands of A/V receivers, as well as with other brands that I do not recommend for the 4-ohm M80s.
Regards,
