The G3 (and I suppose the G5?) have a button on the back to select "active" or "passive" pu's ... so I don't think it's an output issue with why the EMG's sound so good thru the zoom. They just do. ( I'm not normally a huge proponent of active pu's - they got there pluses but also their minus' )
Here's my experience with processors (in general) and I'm wondering if you agree (?): I get a sound I'm real happy with at a comfortable "practice" level ...but when I crank it up for some real fun it sounds thumpy and harsh and needs to be re-tweaked ( mostly on amp eq ). Is that ur experience also - or is it just me? I realize my tube amps naturally break up more at higher volume but it's not a gain issue - it's more about bass/mid/treb at the amp end.
Does ur Peavey have a built-in attenuator or variable watts control?
Alas, I ramble. I will quit now before this turns into a novella. Have a nice weekend- Ken