I love my Civivi Praxis, but I don't know how well bearings will hold up if you're constantly covered in metal shavings.
The RAT I and II in D2 are great knives for the money, and the new KA-BAR Becker folder looks promising.
I think I'd probably steer you toward the Boker side-opening autos (Kalashnikov, Strike, Kihon), most of which fall below $50. Tough construction, reliable action, and better steel than whatever is on your Gerber. I prefer the handles on the Strike and Kihon to the Kalashnikov
Strike Bowie D2
Kihon Desert Warrior D2
Kalashnikov Desert Warrior AUS-8