The Mesa Lonestar.
For whatever reason and totally possible user error, I simply cannot find an IR combo that I enjoy the reference amp with. With that said, I've heard other forum member's clips with that amp sim and it sounds fairly magical. Perhaps I will give it round 2 or 3 with Ares to see what magical sonic bliss cometh from thine Axe-FX.
On the other hand, I find the Two-Rock (Two-Stone) J35 sims are underrated as far as amps used within the forum. I absolutely love that tone along with the Hook 34A/B sims.... just sayin'