Ok....the short answer (not sarcastic!) is that it works for me.
Long answer....before I went to the pre / power amp set up I was running at least two other preamp pedals into the front of my GK1001RB II. I got really used to having the extra eq'ing capabilities (a total of 3 preamps including the amps preamp to work with). I knew when I went with the pre / power amp set up I'd want to use at least two pre amp pedals since I had gotten used to having those eq'ing possibilities. Admittedly it might seem like over-kill using the SCR-DI and MXR M80 together but I love the tones I'm getting. A lot of people don't like the mid scoop on the MXR M80 but I actually like it and use it 100% of the time. Most of my eq'ing is done on the SCR-DI but a little on the M80. My main purpose for using the M80 though is for the mid scoop and noise gate. SCR-DI settings - Drive 9am, Blend between 10:30am and 11:30am (depending on the bass), Volume full, Bass 8:00-8:30am, Mid noon, Treble Noon, Ultra Lo on, Ultra Hi off. MXR M80 settings - Clean volume not used, Volume full, Distortion blend cut, Trigger and Gain (I think full but I can't remember), Gate button on, Bass 9am, Mid cut, Treble 9am, Both Effect and Distortion buttons on. With both these pedal volumes on full and my power amp volume dimed as well I control the overall volume with my SD Studio Compressor pedal.