Contact Lambdalights for an insane mag upgrade.
Also contact Elektrolumens as Wayne builds some insane stuff also. I've got his 'little' Decree XP-G and it simply rocks. Puts out as much light as P7 lights I've got and nearly twice as much light as every other XP-G light I own. For a fee, he will build you a triple XP-G Blaster (magish size) that will pump out over 1000 lumens in a wall of light.
Mac's SST-50 upgrade is a real good one, though it doesn't throw very far and only appears to be really bright when it's very dark as any ambient light swallows up the HUGE spill it produces.
Mac is also in the process of building a completely insane 3000+ lumen mag that uses a triple, triple XP-G set up. Pricey though.
You might want to hold off for a little while as the XM series of leds are due soon and I'm sure there will be a few modders making use of them fairly quickly. I've heard rumors Gene (Malkoff Devices) is working with them now for is new mag drop-in. It's just a rumor though.