... I think you will definately hear an improvement over the 80wpc @8ohms Nad that you have now...
The C372 is rated at 150w/chan, not 80. It is a class G type, and can push sine waves at 150 watts all day long, but with music it's capable of much more, 220w@8ohms, 340w@4ohms. Even pushing test signals the NAD can briefly achieve those outputs, at least until the short term high rail reserves are depleted (which is only a couple seconds), at which point the output drops to the low power rail, which provides 150 watts. For music signals, which only draw from the high rail for dynamic peaks when necessary, the NAD performs much more like a 200+ watt amp. I don't think the OP would gain much by the Adcom or Parasound powerwise; he would have to increase power by an order of magnitude to achieve signifigantly louder spl. For speakers rated at 92db/w/m, the OP should be fine regardless of how loud he listens.
Now if there is a qualitative difference between the NAD and the Adcom/Para, that's another story. Older NAD has a rep for a husky, wooly presentation, but my C372 sounds pretty neutral, similar to the other amps I have lying around.