Glad to read that you like S-Gear so much. It really is a gem, and OlPal is right in his analogy.
I've spent (and still do) an awful lot of time messing w/ amp sims, a/b' ing and mixing and matching. And I still use all of them on and off, but more and more, I'm turning to S-Gear and trying to get back to a "more is less" approach. I used to do my best to try and conjure every possible type of tones out a little Marshall when I started recording, and I feel this approach often works best for me.
The endless possibilities in more extensive collections like AT3 seem to sometimes get in the way when I'm recording. There's just no limit to the experimentation.
The other thing I dig about S-Gear is that it's darn hard to make it sound bad. In other amp sims, there seems to be a relatively narrow sweet spot for each model - where they actually sounds like the modeled amp - but when you start tweaking, things just fall apart. It's almost as if their models are static snapshots.
Unlike these, S-Gear behaves like a real amp. If you push the hi or cut the bass or exaggerate the mid, it will sound like an amp would under similar circumstances. Others tend to just fall apart.