My CS-3 sounds very artificial when I have the compression on hard and I'm strumming loud. However, when I turn it on for feedback purposes, there's no noticeable switch; it just all of a sudden induces feedback with no real effect on the tone.

Actually, when I use it with my MT-2, there's no real tonal difference (aside from the wild feedback if it's set right), even when playing chords or lead. I think it's becuase the MT-2 already compresses the signal a bit.

Anyways, your question was on EQ, and I've done a horrible job of answering it. I will get a Boss GE-7 soon, and then I'll give a review here.