By "reflector" I assume you mean for the LED output? If so, and using lenses (Khatod, Carclo, etc), no, the lens itself "collimates" the light output, directing it forward (a little is lost outside the lens, but reflectors won't help as the lens surface is "reflective" itself, anything that escapes out the sides won't reflect in at the proper angle to be refracted out the front anyhow. As far as recommendations, you pretty much hit it in your post, except that Cree XR-E LEDs are also good with optics, pretty much if doing a new design from scratch, the Cree XR-E or SSC P4 LEDs are the "DIY" standards right now. Luxeons (I, III, V, and K2) are a bit dated at the moment, but still being heavily used due to the many designs already created out there for them. The new Luxeon Rebels are popular but have very difficult handling and mounting requirements and few lenses available.
You can also use reflectors (instead of the optics), and get a few % more lumens (literally 5% more maybe at most), and a different beam pattern (undiffused optics are very precise with sharp cutoffs at the edges of the beam, diffused don't throw as well but are a smoother beam, most reflectors fade a bit more gradually at the edges while still throwing very well based on their beam angles).
Anyhow, a 3-die bikelight with any current LED (SSC for instance) will easily get you to and past 400 lumens, so no concerns there, it's more a preference for what beam pattern(s) and ease of construction that you need to be concerned with.
