Ok, I tried it out - thanks for the "Gain" suggestion!
It's not quite what I'm looking for, and I'm back to Selig gain. The problem is that this "gain" knob can't help me increase the volume of an instrument BEFORE feeding into a compressor that I have chained after it. And I sometimes like chaining instrument->effect->effect as a simple chain. Why? So I can easily Combinate(tm) it in Reason. After all, putting patches in Combinator is the whole point of Reason, right?
With Selig gain, I usually do:
Instrument -> SeligGain -> Compressor
...That way, if the instrument doesn't have a good volume knob, and the compressor doesn't have a knob to turn up the input signal, I have a way to set a reasonable level going into the compressor.
Anyway, it's an edge case.