Rancho 5000's are probably the best of the cheap entry level shocks. They're still a twin tube design, but they seem to work pretty well. Bilstein 5100 series would be a step up and not too much more money. They're a single tube design, a much better performing shock.

Stay away from the self branded shocks from mopst of the lift companies. Trailmaster, Skyjacker, Superlift, etc... They're all rebranded junk.