Personally, I don't care for cheap, rebuilt power racks, since they came from cars that are now really old. I got one with my '37 Oze and I could tell that little was done to "rebuild" it. The steel lines had seen some abuse and black paint was applied right over dirt.

I still have that rebuilt T-bird rack, but replaced it with a new one from Flaming River.

FWIW, it's often suggested to use more caster with a power rack - something in the 3-4 degree range, rather than 1 degree.