I already had 4.56 w/ stock wheels and the truck was pretty damn snappy. When I jumped up to 37" tires it really felt like a pig to me. I wanted to get back that snappyness and have some room to grow incase I change up to 40" tires so I swapped out to 5.13.
Its not like you cant drive on the highway w/ 5.13 gears...your only talking about a few hundred rpm difference.
This gear calc will give you side by side comparison between two sets-
http://www.grimmjeeper.com/gears.html
4 wheel parts had their eaton e lockers on sale for $650 w/ google check out the other week.