I have a 2 pairs of speakers - 2 of them are Yamaha CM12V - rated program at 500W daisy chained together on ch 1. The other pair of speakers are a Yamaha SM15111 - daisy chained to a Yamaha C115V - both program rated at 500W - on ch 2 - all the speakers have nominal impedance of 8 ohms. If the QSC MX1500a amplifer is rated at 330W per channel at 8 ohms, am I underpowering the speakers?
Yes you are but how much is the question. That depends on what you mean by "daisy chained".
If that means each pair is in series then you are presenting 16ohms to each channel which is lowering the amp to 165 watts per channel. Way lower than the 1000 watts per pair that they can handle.
If that means you have each pair in parallel then you are presenting 4 ohms to each channel which is raising the amp to 600 watts per channel. That's much closer to the maximum that the speakers can handle. If you got a 1000 watts per channel amp into 4 ohms then you would only get 2-3 db more output from the speakers. Not a big difference so don't worry about it.