Well the reason I asked about what you were using it for was almost none of the 3 knob boutique models are really good for that as they let too much bass through to be useful into your Mesas, Peaveys etc. A very lean pedal, like a TS9, or one with a nice EQ section is best for front end enhancement. For example, the Xotic RC and AC boosters are based on TS circuitry, but with a Baxandall EQ section. Some people like a lot of dirt out of the pedal, some people don't but the main ingredient IMO is that sharp bass cut that lets the bass stay tighter through the gain stages. It's not the absolute best way of getting tighter bass response out of a high-gain head, but it's still very effective, widely used and coupled with a boost. Of course you'll be throwing the bass knob on the amp up more to compensate, but that's just how they work together for metal.
Good luck in your search.
