I had a Spider Jam for a while, and found that plugging the POD into the CD/MP3 input with the POD in Studio Direct mode sounded best with that amp. You are basically bypassing the amp modelling in the amp and just using the POD that way.
Some of the later Spider amps have a way to disable the amp modelling when you power on the amp, so you can plug the POD into the amp input, but I can't remember how.
If you are not using dual paths, try muting channel B in the mixer, and set the pan on channel A to 50%, this really helps to reduce the volume of the DT.
