I've been a large fan of Soilwork for a while now, and I've recently noticed that they tune down to B with their guitars. Now I've pondered over this fo a while, and realised that B is the note which is on the seventh string of a seven string guitar. So I'm sat here thinking, why not just get seven strings? You've sold enough albums to buy yourself some nice ass guitars, so why the hell not? surely all that detuning is bad for your guitar.
B isn't bad for your guitar. I have played my 6 stringed BC Rich (which is 14 years old) in B for the last 3 years. No truss-rod problems.
Also, you can use a 6 stringed baritone for low stuff without even thinking about a 7 stringer.