2014WhiteSierra

hey guys, new to the forum, I just came out of a 2007 Avalanche LTZ with autoride air suspension and Michelin LTX on 20's which rode beautifully. Now I have a 2014 Denali 6.2L with 20's. Just put the same Michelin's on the denali, 275/50R20 which helped a bit (32-34psi) but the ride is just way too stiff and rough for me, it feels like a 2500 or 3500 to me. When I make turns at intersections with potholes it loses its composure easily, jitters and hops all over the place. I feel like a bobble head driving around town. I had an aluminum folding ramp in the bed, when I hit a few small bumps I could hear it going airborne and banging all over the place, sounded horrific. I've read many threads here, but before I pull trigger on shocks I was hoping for a few opinions. I really don't want to put 200-300lbs worth of sandbags in the bed. I just ordered the sulastic shackles for the rear leaf springs to help isolate vibration. I'm about to pull the trigger on rear shocks, I see alot about the bilstein 5100 here, but bilstein also makes much better models too, why only the 5100 discussed? I also see the Fox IFP, the King Shock 25001, & the pro comp as well... price is important but not a deal breaker. So which shock will give me the softest ride? Not worried about payload or towing. Do those remote reservoirs I see on some of the shocks help with smoothness? Thanks all.