OP:
If you want to use an EQ in the loop for soloing not because you want to get a volume boost, but because you want to change your sound, consider this alternative (it's what I do):
For rhythms on channel 3, I use a high output bridge pickup with the GEQ on.
For leads, I switch to a midrange-heavy, smooth neck pickup with the GEQ on. I sometimes add a touch of smooth overdrive in front.
The result is that without turning on and off the GEQ or using a second EQ, I can get two very distinct tones from channel 3.
I also keep a subtle chorus in the loop, which sometimes I turn on for leads (along with some delay). I normally hate chorus with distorted guitar, but I've got an MXR stereo chorus, which has EQ controls for the effect. It allows you to dial in a very smooth sound (with an attenuated, rounded high end) and keep the effect subtle.