I just recently checked out Waves Superrack Performer. In theory the USB connection from the Qu24 should work as an I/O for the Superrack.
My question now (I havent tried it yet):
Does it really work?
How do I rout it correctly?
Has anyone tried it?
I haven’t tried it either, but got this reply from Waves tech support:
Looking at the A&H QU-24 manual, I can see you can use the USB-B with their Asio/Core Audio driver to send and receive 32 channels.
Per the manual - USB B Streaming – Connect an Apple® Mac or Windows® PC computer to the rear panel USB B port to stream up to 32 channels of audio in both directions
SuperRack Performer should work perfectly with the A&H driver.
So I may get it. It’s US $99. If I do I’ll come back and post the results.
Update:
I have since tried it and it sort of works.
You are able to send audio to Waves Superrack from your Qu Mixing desk just like you would send it to a DAW. The problem is routing the audio back into the desk.
Qu Mixingdesks neither have an insert point that you could use to rout audio back and forth, nor can you use the preamp while then processing the audio coming back from USB (like you would use Waves with an X32 for example).
The only solution I have found sadly is using the input on one channel and routing the processed waves audio back to a second channel. You therefore can only use half the channels on your desk if you want to rout all of them through Waves.
If anyone finds a work around to this problem feel free to share 
I have performed many virtual.soundchecks on the QU series using all 32 channels back and forth to any DAW. DAW needs to be setup with input to channel one and output to channel 1 and so on. The qu needs to be setup at each channel where you change the source. To record the channels on qu are set to local inputs or DSK if you have a stagebox. To playback from DAW, you set each channel source to USB. It’s that simple.
The QU can only have input either as the head amp or from the USB. Theirs is no way to use both so you can have live waves on the same channel. (No insert from usb/ computer so no way to have external processing)
Chris