I don't own any of those lights (so the following is pure speculation), but to compete against a HID... the Mega6 might have a comparable total light output, but the Stadium could be better focussed. Burn time of 6*5W in a 6D maggie could be around 10000/(6*750), roughly 2 hours, depending on how they're driven. And I don't think (please, correct me if I'm wrong) that the Mega6 is intended for long-time use under full power, somehow you'll have to get rid of the waste heat (yes, even with LEDs - especially with LEDs!).
But if you want total light output: there's a German electronics store that sells 10*Luxeon linear arrays. Mount one or two of those to each side of the fork, and you'll likely get a very nice area light /ubbthreads/images/graemlins/cool.gif
Bye
Markus