If you're OK w/ plastic: per flashlightreviews.com, Bright Star Responder 4AA & Princeton Tec Surge out-throw the Peli. Also, maybe a UK 4AA with 4 watt lamp from brightguy.com? All would have advantage of cheap AAs rather than CR123s.
I had an M-6 and just couldn't get used to 1 hr. runtime on 2 CR123s, so I no longer have it. Am optimistic about the SL Strion on its way this week, but it's over your $50 limit. BTW, I haven't owned the 1st 3 I suggested above, just read about them. But, if you buy one, please post your impressions!