The Aleph is the top, but you can sometimes get good deals on E-series lights on the B/S/T Lights forums - and many of those will accept mods like new heads (KL1, KL4, KL5), new tailcaps (Mc2ES is one I'd recommend), new bodies (Balrog bodies, for example), and so on.
While you can get a McCapsule for a Longbow to improve the LED, I'm not sure if that'd fix all the issues - by the time you've bought a McCapsule and a SOX17A reflector, you've spent about $130-140 on the light, which you could've put towards an Aleph or a SureFire and gotten more options for modding. Heck, buying a pocket clip is another $25, which puts you just $25 short of an Aleph, and definitely is enough to buy a brand new SureFire L4 or maybe a used L5 light. Longbow's a decent company with a decent idea, but after everything I've heard of their regulation and the tints of some LEDs, I'm not sure I'd be willing to spend the money to make it a good light (pocket clip, reflector, UCL lens, McCapsule). I'd either just save up for a better light, or else buy a cheapie like a Q-III and switch out the emitter as MilkySpit and 4sevens have done.
The Q-III has a boost circuit, not a regulator - so it won't regulate at all. It'll give you an hour's runtime if you have a bad LED (L-binned and up), or relatively good runtime (90-100 minutes till 50% brightness) on a K-binned LuxIII. The 'pocket clip' is also crap - it's set up too low on the bezel so the head sticks out an inch or more from said pocket, and balances the light rather poorly as a result. It also isn't tight enough for serious pocket-carry in that configuration - and I'm not sure I'd trust it on the bill of a cap. The only purpose the clip serves is to keep the light from rolling around, and I'd rather stick a lanyard around it to keep it from getting lost.
The Aleph you can buy from McGizmo for $195, which means everything's assembled and the battery's ready to go.