Inverted Amplifiers

circuity. Each stage of amplification inverts the signal. So, (Conrad-Johnson comes to mind) designers who use a three stage design have inverting. Dudes who design four stages in the circuit do not invert.
Inverting is no big deal. The same effect would be to reverse the speaker 'plus'/'minus' wires.
If you are worried that you would not know.. If you cannot straight-up hear polarity of recordings.. then 'why-worry'!!!!
Few designers use circuits that leave polarity inverted. So (usually) the ones who do will say they invert. Most everyone does not invert, so they do not bother to say they do not.

If your amp inverts and your pre doesn't just reverse the lead as E. suggests above, red to black etc. This leaves the whole question of recordings which are made with reversed polarity ; my DAC has a reversal switch and occasionally it makes a considerable difference. Most of the time it does not.

My concern is with the proper setting of the powered subwoofers that are part of my speaker system. The speaker manufacturer's instructions state that toggle switches on the subwoofer modules should be positioned one way if the amplifier inverts and the other way if the amplifier does not. But the speaker manufacturer's manual does not tell me how to tell one type of amplifier from the other.

In the following thread you'll find several suggested methods for setting the phasing of subs relative to mains, which is what it sounds like you are trying to do:

http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1258010309

Keep in mind that both possible settings are probably compromises to some degree, and are influenced by the physical positioning of the subs relative to the mains.

Regards,
-- Al

My RELs instructions indicate that this is best set by ear, in my case out of phase sounded better. The Sumiko site has their set up guide for subs which is simple and helpful.