PB superflash is all you'll need. Get 2 of 'em if you want. But as long as you have batts that aren't dying, PBSF or MARS 3.0 is hella bright at night. I see them a lot around here, and I never fail to be impressed by their flash.

I've got an 18530 powered light (Magischine) which is much brighter than PBSF, but it's frankly overkill, IMO. PBSF is more than enough from what I've seen around here, even in traffic (and there are a lot of night commuting cyclists in Norcal.)

OOPS - edit - forgot you were talking DAY use. That's different. Dinotte.