I mentioned Plover and steno in my linked comment. Basically, classical stenotype and other similar syllabic two-hand chording systems are a big bag of hurt, and probably not well-suited for anything except transcribing spoken English (or whatever natural language your steno system is designed for). A more orthographic system like Velotype http://www.velotype.com/en/ / Veyboard http://www.veyboard.nl/en_main.html is probably better unless you need to optimise for the last iota of transcription speed in one specific spoken language, especially since most of us will never reach professional real-time transcription speeds no matter what keyboard we use. (And OTOH, Velotype is apparently fast enough to be in use for real-time tasks in the Netherlands.)

EDIT: Also, most people would probably be better served doing something about the time they spend moving their right hand between keyboard and mouse than increasing their typing speed.