I have pretty much all that you've listed. MXR M-80, MXR M81, B7K, and a Sansamp RBI rack unit.
I'll try to keep this short, I know I tend to ramble, but it might help you with the rabbit trail I went down similar to this.
I started out looking for drive and grit. Had a Boss ME-50B, didn't like the distortions/OD on it.
Got a Sansamp Bddi (3 program pedal). Totally dug the tone of the Sansamp, it really gave me what I was looking for. On a whim to try new things, I got the MXR M80 distortion pedal. It's got 2 channels, one is Effect, and the other is the distortion. You can turn the gain down really low on the distortion side to make it give a small amount of grit, and have two useful channels.
The Distortion on the MXR M80 is more of a love/hate thing. I find it to be VERY aggressive and not really what I was looking for. In a band setting, I found that it didn't cut through the mix.
What I did like on the MXR M-80 was the clean effect with the "Color" option. It really makes it sound awesome. So I found out that MXR recently came out with the M-81, I figured it was like having the MXR M-80's "Effect" channel all in a controllable pedal, with complete control of the mids. After about an hour of tinkering with both pedals, I realized that the "Color" option on the M-80 is a scoop. I was able to replicate the M-80's sound through the M-81 by boosting the lows and highs and cutting the mids. Sounds great, but live, it'll just drain me out of the mix.
So I completely ditched the M-80, and switched over to the M-81. I use the M-81 not as a tone shaper, but more of a volume/bass control. When my guitarists are soloing or when there's a clean part in our songs, I sometimes find that I'm a little too boomy and up front in the mix in our jam room. So I set the M-81 to drop the bass a little, and lower my output to where I sit in better with the rest of the band.
My currently tone is a B7K that's always on so that I can sculpt the EQ, and then I run the blend @ 2 oclock, and the drive down at 9 oclock. that is pretty much my tone 95% of the time. On songs where I can run the drive high for the whole song, I up the drive and lower the level a little to keep it balanced. On songs where I keep the B7K's drive low, but I need to add drive mid song, I have a Darkglass VMT with heavy drive and heavy blend. Stacked, the two work well. But I'm going to probably replace it with a B3K.
One thing I will say about the Sansamp line, if you get the BDDi or something else, you're only going to get a bass and treble control. I got the RBI rack unit because it's got a mid control, which I boost. So be weary of that. I think to boost the mids on the other pedals you're supposed to cut the bass and treble and it'll bring the mids out. I was using the Sansamp Rbi with my B7K on a lot, but I've found that I can run just the B7K and my tone cuts through a little better since the Sansamp has a little bit of a natural scoop to it.
I also have a vid online going through the pedals. It's kind of long winded, but I intend on cleaning it up and having a better presentation of the pedals. I haven't removed it yet, but I probably will once I have a better plan on how to document it and put it into a nice concise informative video.
My opinion, I'd highly suggest going with a B7K. You can get the eq the way that you want it, and get some awesome drive out of it. The blend and level controls on the B#K work a bit differently than most pedals and give you a lot of options to sculpt a tone you're looking for.
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