New Shocks, What kind??

I was told that I need new shocks on my rear because they are leaking. However, they said my front ones were fine (the front are stock and the rear are after market). Would you replace them all or just replace them as needed? Also what are the best brand of shocks to put on? I really don't go off road a whole lot and would like a smoother ride than I have now but still be able to go off road when needed. Thanks for helping

 

Bilstein 5100s, all four shipped for $282 from downsouth motorsports. Fronts can be set at 0,.85, 1.75, or 2.5.