attenuators and potentiometers

I have a wonderful Conrad Johnson Motif MC8 preamp and a wonderful Accuphase P-300 power amp. On all my sources, if I turn the CJ's volume pot up beyond 9:30 or 10 o'clock, it is very, very loud. Often normal listening level is at 8:30 or so, maybe 9:00 for phono. Now I know that volume pots tend to be at their least balanced (l/r signal) at the low end of their range, and I actually think that at lower volumes I sense more coming out of the left speaker than the right, though I cannot say for sure that that is an effect of the pot, instead of the room or some other link in the chain from groove (mostly vinyl) to ear.

Now the P-300 has a switch that limits power output to 50% and 25%. This allows you to use highly efficient speakers safely. It would also allow me to turn up the pot on my preamp. It also has dual level controls. Till now, I have used the amp only at full power, with the output controls to maximum, on the assumption that it's a straighter wire, as it were, that way, so a cleaner signal, than if I use the power limiting switches; also that it would diminish dynamic headroom, etc.. But I am not sure that these are safe assumptions.

So my questions is whether, from a theoretical standpoint, and also from anyone with knowledge of one or more of these pieces, using the attenuation switch on the P-300 should have any effect on the waveform that stands to compromise my sound -- so that it is not just a pure benefit being able to run the preamp volume pot wider open.

In short, theoretically, does using the attentuation compromise the quality of the audio signal?

Speakers are Thiel CS2 2's, if that matters. Easier load than most Thiels.

Thanks!