As far as I know, the brightest 2xAA light is the EagleTac P20A2 MKII. It will run you about $60 though. I purchased one for my Dad from Flashlightsngear.com (good shopping experience), and with the CPF member discount it was just short of $60 shipped.
It's an outstanding light that has a lot of "wow" factor because it's built to throw a bit more than most other offerings, so the hotspot is intense. The spill and transition are still very nice and smooth though. It's a bit bigger than other offerings, but it looks super cool, and is still quite small for it's impressive output on ~3 volts
I had it side by side with a Quark AA2 (also purchased for my Dad), and it is definitely brighter, although not by a whole lot.
Depending on his preferences for user interface and modes, I wouldn't hesitate to buy any of the following. None will be quite as bright as the EagleTac, but all will be so close as to not really matter unless he needs longer throw capability.
1) 4Sevens Quark AA2 - VERY versatile, with lots of modes and interchangeable parts. Smaller than P20A2 - ~$55
2) 4Sevens Quark AA2 Tactical - Different UI and clicky switch to AA2, otherwise the same. ~$55
3) Fenix LD20 - Great build, similar UI and modes to Quark AA. ~$55
4) Quark AA2 Turbo (tactical or regular) - Same as the above Quarks, but with a big head for excellent throw. ~$65