i've owned pioneer, onkyo, and yamaha, and i honestly liked the yamaha the least....
they all have very unique sounds, the onkyo's the warmest sounding, not great for music, but movies were terrific...
yamaha was too bright sounding for me, i know that's what most people like about them, they 'sound' the most high-def, but i personally ENJOY midbass.....
the pioneer was the best combo, i would say it was the most neutral sounding, sounded, well, like most stereos...... Best D/A processor of the slew, tho..
I WILL say, however, that i enjoyed listening to the yamaha the best of the 3 on headphones..... Their headphone preamps are 2nd to none, and the simulated surround (forget the actual name for it) on the headphones is very impressive....
The yamaha and the pioneer also both had self-balancing speaker levels, with a microphoe you placed near your seat, which was a neat feature....