I own two GLD80s. I have spent a couple shows on the X32 in monitor world. I have no issues with the sound quality of the X32 and didn't notice the circuitry to be noisy.
The GLD does sound fantastic but unless you have super golden ears I don't thing that you'll notice any differences between any console other than how the EQ works or how natural and real sounding the effects are. I imagine that the delay caused by some routing configurations might make one console sound better than another.
The big difference between the GLD and other <$15,000 consoles is the flexibility with routing. If you need the flexible buss structure and ability to move faders to different layers and the ability to have graphic EQs without using up FX slots the the GLD is the console for you.
As far as GLD80 vs GLD112, I don't need the extra faders and prefer the compact size of the 80. Your application may be different.