I see no point to having switchable biasing. I would't waist my money on that.
I actually have an Xforce TNT 600HD. I bet it is a great amp but I blew it up the first day. I'll have a better idea of how good it is when it gets back from repair. I am not going to push it for its full advertised output again. Lack of experience on my part. I think I would rather have something that I don't have to drive the snot out of to see 800W. I also would prefer to have AB instead of B class.
If you blew an amp like that on the first day, you have more issues than overdriving going on. Sounds like an antenna issue because these B biased amps can take abuse.
I owned a Magnaforce 600 and drove the crap out of it with Magnaforce 200 2x2290....never a problem in the 8 years I beat on it.