I never had any of the Diamond products, but the EverLED on three cells isn't as bright as a direct driven Lux III on three cells. The potential problem with the EverLEDs and Diamonds is heat. If you go the custom built route, there is a thing called an OSink or Hotlips both of which do a great job of transmitting the heat out to the body of the light rather than keeping it right at the bulb holder. I'm not saying the EverLED and Diamond products aren't properly heatsinked, but I don't see how they can last as long as one that uses an OSink or Hotlips.
On 2D Mags on a relative budget, I usually like to use a TV1L Lux III emitter and three C cells and you should get close to 4 hours of good brightness on the 3 C cells.
Of course, the even cheaper route would be just to get the LEDBeam 3C light. Nearly as much throw (probably 80% or 90%) as a Lux III-modded Mag for only $25 shipped which is less than the EverLED. If you insist on rechargeable cells, just invest in some good high mAh C cells (not the crappy 2500 mAh Energizers) rather than using the AAs.