Hi Shadow_oo00

I not sure which 5 watt Terralux replacement bulb you are thinking of purchasing but you may be interested in the TLE-6EXB TerraLUX MiniStar5 SSC P4 U bin LED upgrade for 2-3 C/D cell Maglites

available at
http://www.batteryjunction.com/tle-6exb.html

Its rated at 3 W using a Seoul P4 emitter but will be brighter at 150 Lumen than other 5 W Luxeon replacements. Will improve battery life considerably and be brighter.

Oh its the same price also as the ones you've mentioned at Wallyworld. BTW 150 Lumen is pretty darn good.

The reason I would also go for a lowered powered but more efficient emitter is also the issue of power rating and the ability of the 2D maglites to dissipate 5W without proper heatsinking