I like my TC BG115. Never played through the promethean. I like the tone just fine out of it. Good EQ, like the TubeDrive, dont use other effects. Lots of volume for a pretty small and lightweight cab. I do wish I could attach it to another cab but I really dont need that. I plan to buy a much larger set up and head down the road so this works fine until unreasonable desire or actual need takeover. Determining whether you'd like to buy a cab and build from that or get one and have it be stand alone should be one of your questions. All in all Im a happy customer.
EDIT: Oops we're talking 112. w.e
Phil Lesh Appreciation Society Member #87
Gordo Club Member #41 Wisconsin Bassist Club #152