You know, I could take or leave Extreme but I've always loved Nuno's sound and playing. Years after I first heard the guy, a buddy who toured with him told me "dude his sound is nothing but a JCM 2000 and a RAT pedal" and I didn't believe him at the time. Well now he's done a bunch of interviews confirming exactly that and it's become common knowledge and boy do I feel like a horse's patoot. So I tried a RAT as a boost pedal, mostly the same way he uses it, which honestly is basically the same way all the best overdrive -> distortion tones are achieved: barely any drive, tone to taste, level in the middle, and its become one of my favorite boosts.
I picked up a real one because they're about the cheapest pedal around, and turns out the one in the Axe-Fx is very, very close to the real thing.
Seems like the RAT is a pretty great boost pretty much no matter what you put it through. Here's Fractal's RAT drive model running out into a real Peavey 5150 -> Surh RL, and back into the Axe-Fx for the Cab block and some delay. Sounds good to me!: