Here's my example of knowing the Alembic preamps are really hot. In the 1.5 years I was using my Eden WT300 with my Jazz bass with EMG's, the fan never went on. I plug my Alembic in, and the second time I play it, the fan comes on. And I'm not even playing loud.
Knowing that, I get my Skylark, and my fuzz's sound bad. But, it makes my old Bassman head just sing with overdrive at about 4 or 5. There's no way my Strat nor Paul are going to make that head sing at the same level. So if my Skylark is doing that to my Bassman, what is it doing to my fuzz boxes? Of course they can't handle the output of the preamps.
I plugged my Strat into my head, put it on the bridge pickup, strummed it hard, and got a level. Plugged my Skylark in, bridge pickup, strummed - defintely louder. Turn down the preamp to match. They are turned ever so slightly from off. Because the preamps are designed correctly, you don't lose any tone from playing them at that low of a level. Plug in my boxes, they all work.
Make it as difficult or complicated as you want, but this is not rocket science. Just a little logic from my experiences with the preamps.