What do you think of Torsion Axles?
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There's a set on that site you linked that include 6x5.5 hubs & electric brakes for $400.

With the torsion axles you don't need the leafs or any of the complexities with them however, I don't know how tough they are or how long they'd last off road.

It's what they use in the trailer above so I would assume they're pretty reliable but don't know for sure.