MiniMag mod noob, plz help

I'm new here but have been reading the forums for a few weeks.
Can anyone tell me what is the best LED to use (3mm please, I don't want to void my warranty), because I have read somewhere that a high mcd LED can be dimmer than a low mcd LED.

I'm looking for a hotspot and little/no spill on the stock reflector.

Should I just go with a 3mm Nichia? Or shell $5 at RadioShack for a blue 3mm?

Also, where can I buy an LED that can be shipped in the US for less than $10? (It's a $10 light, I really don't want to spend more than it's worth.)

Is there a difference with another reflector or optic vs. stock?

Yes, I realize I'm asking for the "best car" or something along those lines, but someone has to have an experience with LEDs, especially on a CPF, :twothumbs

For $10, you could get an XP-E of DX. If you just use 2 AAs, you probably won't need a heatsink beyond the star. This might not focus too well though.

3mm LED? Does that even exist?

Nite Ize and Terralux have, between them, half a dozen LED upgrades for minimags. From 3x5mm LED heads onward. Couple of combos too (LED plus tailcap switch).

Problem with minimags, imo, is that you have to loosen the head to turn the damn light on. The loose head bugs me to the point I cant stand the light. Tailcap switches mitigate that a little, but the sensation of "not solid" remains (yeah, yeah, I'm a perfectionist freak). So, after a lot of experimenting and tinkering, I just decided minimags where not for me.

That said, I still keep 2 of them:
- at home I have a red body with red LEDs from Nite Ize plus clicky switch from Terralux, for navigating at night and not waking up people
- in the car I leave one with the Terralux 50lm LED and Nite Ize IQ switch (multimode) plus magnetic clip and red police wand diffuser.