sounds like the problem is gain staging.

Do you have the GT hooked up to the Behringer pre ?

That is a bad move as you really want to keep your signal path as short as possible. You also want to try to only use one peamp. Sending the signal through more than one can make it noisy, There are pres on the desk as well.

If you absolutely have to use more than one pre then turn the first one right up and all the others right down. The idea is to et your signal as hot as possible as soon as possible with out it clipping.