I currently use an Opalec Newbeam upgrade in my MiniMag.
This is a fully regulated (current+voltage) 3xled module. It gives a very nice flood light. You don't need the reflector anymore in the Minimag.
Very good for camping and close-up work. On 2xAA it runs at about 10 hours at full brightness. When it runs out of battery power, a small red-led indicates that.
What I've also used is TerraLUX MiniStar2. Now my brother-in-law has it.
This is a Luxeon Star led (like you have in your Arc LSL), which comes with a modified reflector. This one has much more light output and because you can still use the reflector, it has more throw (a narrower beam). Battery life is shorter of course then the Opalec.
Terralux also recently made a MiniStar1, which has 4x3mm leds. I haven't tried that one out yet.
What Rorschach is suggesting are the MadMax (MM) and BadBoy (BB) modules offered by TheLedGuy. There's a forum on CPF dedicated to these modules.
http://www.candlepowerforums.com/ubbthr ... wichShoppe
I honestly still haven't figured out if these modules are ready to insert in a MiniMag, or if other stuff is required.
Another good upgrade for a MiniMag is a kroll switch. That's the same switch that's on your Arc LSL-L. What you can try is unscrew the rubber switch from your Arc LSL. Then unscrew the tail cap of your minimag and screw the rubber switch on the MiniMag. Now you have a clicky-MiniMag
Kroll switches are availble from the same site that sells the MadMax & BadBoy stuff.
My ideal EDC would be an Opalec module that run's on a 1x123 battery in a very small housing, like this one here: