you should be fine. An 8000 lbs winch, such as the Warn M8000 for example, will still pull 6200 lbs on it's 4th wrap. If your JK weights 5K then you are not exceeding the capacity. A 8K winch will be a little faster and pull more amps than a 9.5K winch would on the same pull becuase it will probably have less gearing.
It's always good to carry a snatch block for those hard pulls though...
2009 Rubicon Unlimited, FLAME RED
37's on WE beadlocks. ProRock44 w/ARB, RCVs, spyntecs, PSC hydro assist. Rear D44 w/35 spline ARB. 4.5" Poly/TF lift.