Por-15 is good stuff. But so is rust-oleum. It all comes down to how well you prep the metal.
And you definitely don't need a gallon of bedliner for one bumper. A gallon will do 2-3 coats on a tub. A half gallon or a quart is probably more what you need.
OME 2.5" coils and Nitro Shocks, Metalcloak front track bar, JKS Quick discos, 33x12.50 Goodyear MTR's w/Kevlar, 15x8 Pacer wheels, thedirtworx rear tire carrier