Quite a few people use higher power flashlights- most of them post about them in the Electronics forum. Fenix lights were the rave, only to replaced by the P7, then XP-G, and now the XM-L.

I take it that your Terralux 220 is rated at 220 lumens? Adding another would double that to 400+, which would put in the ball park of a bunch of the lights that claim up to 900 lumens but I gather deliver closer to 400-500 in reality.

There is a new light (or I just heard of it last week, anyway) from Philips that is a dedicated bike light. Not as powerful as a Magic Shine, but focuses the light way better for road riding. http://www.youtube.com/watch?v=lej8pbR5RDQ