Packer(fan, I presume), welcome. The loudness level that you use, the dynamic range of the program material and your listening distance(a more significant factor than total room volume)are the primary determinants of how much power is needed at your listening position and suitable speakers to produce it. Unless the level is extremely high and the distance quite long the M22s, with the fine sub you've described taking most of the heavy bass load off, should be very satisfactory.
In any case don't pass up the exceptional QSs for side surrounds. My first pick would be M22s plus QS8s and no center speaker. If tower speakers are wanted, the M60s plus the QS8s would still fit your budget if you order from the Factory Outlet(new speakers with a slight cosmetic blemish)with a 10% discount.
Unless again the sound level would be extremely loud and the listening distance long your 788 should drive your Axioms with ease. There are tendencies to overestimate, sometimes to a gross degree, the amplifier power actually needed.
