Why not just get the XL50? What do you do with your flashlight? Anything extreme like night time hunting...
I recently went on a Maglite binge and went through determing, "which should I get, the XL50, XL100 or XL200" ? What I determined was, the XL50 is the simplest and is a fine flashlight. The XL100 has a bunch of gadgets I probably don't need/want, personally, but that are neat. And the XL200 is the brightest, more for sportsmen and hunters. If you already have an XL100, I'd recommend just getting an XL50. It's a fine flashlight. I received it for Christmas and I simply can't get it to run out batteries with daily use... it's starting to blink due to low volatge but then the circuitry must have a capacitance system because a few blinks and it's steady again. It's amazing, really.
If you want something a little different, get an AA Mini Maglite and then upgrade it with a TLE-5EX. I'm in the middle or doing that for my wife
. There's a British video on youtube that shows original vs. upgrades for the MiniMag...
http://www.youtube.com/watch?v=lF-wrbJTQyo The original is on the right. The Terrelux 5EX is all the way on the left. Don't bother with the middle upgrades... first and 2nd gen upgrades...
If I want something really bright, I go get my blinding 6D Mag with a Terrelux TLE-6EXB and a 1,000+ foot throw.