Cam -- No, I think that Shadorne was speaking in more general terms, and the issue he cited about overdriving consumer-oriented gear with pro-oriented signals is not applicable to your situation.
It would be a concern if the outputs of a pro-oriented source component, or a pro-oriented equalizer or processor, were fed into the line-level inputs or tape inputs of a consumer-oriented preamplifier.
In your case, though, you are dealing with a preamp-to-power amp interface (meaning higher full-scale voltage than consumer source component line-level), and with both components being consumer-oriented. Your power amp has an input sensitivity of 2 volts in unbalanced mode, or 4 volts in balanced mode. That will certainly not result in clipping or overdriving when being fed by typical components.
In fact, the opposite will occur to a minor degree if you go with the adapter cable approach -- you will have to turn the volume control up by 6db relative to where you set it when using the power amp's unbalanced inputs. That is because instead of feeding the amp with a balanced pair of signals that have equal amplitudes and opposite polarities, you will be substituting ground (0 volts) for one of those polarities, resulting in the difference between them being half as much.
The only negative effect that could conceivably have would be to increase background hiss slightly, but unless something is marginal in your system to begin with that will not be a perceptible effect. You can test that right now, in unbalanced mode, by simply turning your volume control up a little bit from where you normally set it (corresponding to a 6db increase, as best as you can estimate that), with no music playing, and seeing if the hiss level becomes objectionable.
Regards,
-- Al
