What tires are you running?
When I switched from dismal Goodyear Wrangler RT/S to Michelin LTX M/S, my ride improved A LOT.
When the Michelins were eight years and showing slight cracking from vibrations, driving, weather, etc, they were replaced with Firestone Destination LE2. Ratings on Tirerack were very close to the original Michelin LTX M/S.