Is cost an issue? I understand it can be. The Q3 wins bang for the buck. It's untouchable for what it delivers. Adequate regulation, reasonable construction and a Lux3 up front. NOTHING in its price range comes close. If you take advantage of 3rd_shift_light's "binned" (sorted by tint) Q3 offer, it's unbeatable.
If cost is no object, 3rd-generation KL1 + E1e, with Surefire's legendary KL1 buck/boost/everythingandthekitchensink circuit. Precision regulation as opposed to a cheap Zetex circuit, eats ANYTHING from 2-9V that you can feed it. Rechargeables, NiMH, lithium ion, alkaline cells, if you can cook up a battery holder it will eat it. Mod it to a SO17XA reflector and tweak the drive current if you desire. Get a Z57 PROPER (instead of reverse) clickie, plus true HA3.
Of course, you lose BIG time in the pricing department /ubbthreads/images/graemlins/tongue.gif but if you are the kind who brooks no crap and makes no compromises, you know what to get. You may want to take out calipers and measure you wallet in advance and take pride in that reading, for once you get started with the Surefire stuff, it will never that fat again /ubbthreads/images/graemlins/grin.gif