What do you mean by "high gain"? What type of music and songs are you referring to?
Generally, I don't use Peavey amp sims or similar models because they tend to be too much for my taste. However, since you mentioned the Placater, your definition of "high gain" might not be too far from mine.
In that realm, I've always loved—and still love—the Bogner Shiva (German Mahadeva) amp model. However, especially when using humbuckers, I prefer to cut the lows slightly in front of it (using an EQ block) because it has a rather complex tone with rich low mids. I also love using that amp model for clean tones by keeping both the drive and mid levels very low in that case.
On the other hand for "real high gain" the two Revv amp models are very interesting imho, but I have to say it again, I'm far from an expert on that field.