Mark,

The STEREO mode on the 45TX leaves all digital-domain processing turned on (obviously except for the matrix surround processing). For example, the MCACC level/delay/EQ adjustments for the front L/R will be used, and the high-bit/high-sampling feature will stay on if you have turned it on. Also, in my experience, the STEREO mode seems to play it 3-4 dB louder than the DIRECT mode.