I have a similar problem 'round here. I use my electric guitar that's equipped with a piezo pickup with the KPA. Each signal, magnetic an piezo, has it's own cable. So it's like having two guitars at the same time...
I run the magnetic signal straight in the front input. The piezo signal goes through a buffer (I use a Lehle Sunday Driver XLR for that) to lower the impedance first, then into the return input of the KPA. When you activate the mono loop in the stomps section, you can add your second guitar to the signal of the first guitar - from 0 to 100 percent. Sounds really great.
