Just FYI...if you're seeing bike lights / torches advertised with Q5's and P7's...it's kinda "old news". The Q5 is especially outdated.
A really killer setup is the XP-G R5, XP-E R2, or the newest XM-L emitters.
I machined some pretty gnarly lights with the XP-G and XP-E's.
The XP-G works best with Regina reflectors. I was building some "double barrel" designs that were seriously P7 killers. They were so tiny and lightweight...yet you were getting a super efficient beam with the Regina's.
A second setup with XP-G's that worked well was a 20mm 3-up board with Carclo Narrow optics. It was a pretty good all'rounder, but not quite as punchy as a dual Regina setup.
The 20mm 3-up XP-"E" setup was an incredibly fun board to play with. It had alot more throw with a narrower beam than the G's.
The newest emitter to keep your eyes peeled for is the XM-L. I've moved to a new city, so I haven't built anything since last year. I don't have experience with the XM-L, but the spec's look pretty awesome. We're talking a true 1400 lumens out of a light the size of your thumb. Not the 600'ish that the Magicshine actually puts out. (though it's advertized at 900)
Just food for thought if you're window shopping.