92 Sub rides like a haywagon, help!

Hi folks. Recently got a 92 Sub 3/4t (2500) 4WD 454. I replaced the shocks all around with the cheapest stuff Pep Boys had, which turned out to be "Monroe-Matic" shocks in the front and Monroe Sensa-tracs in the rear.

I tried going over some speed bumps quickly as a test. We could hardly feel anything in the front-- but the back seat feels like a trampoline.

So my question is, what shocks should I get to fix this problem? I am looking for something that will give a great ride, but also be able to handle off-road with the heavier 3/4t leafs in back. Should I go with reflex or monotube? Should I change both the fronts and the rears, given that the front seems OK now (i.e. are they going to affect each other, off-road)?

I have found a few shocks that look promising:

Twin Tube:
1) Rancho RSX Reflex
2) Gabriel "Ultra LT" "G-Force"

Monotube:
3) AC Delco Monotubes
4) Bilstein "Sport" Monotubes
5) Bilstein "Heavy Duty" Monotubes
6) Gabriel "Max Control" Monotubes

Another thing to keep in mind -
Suburbans get real touchy in the back when there isn't alot of weight back there. I can feel a major difference between a full tank of gas and an almost-empty one.

Yeah, when we did the test, I actually had some significant weight there. About 400 pounds in back including rear seat passengers. Gas was about 1/4 tank though.

Still, I definitely want to get some shocks that will work significantly better, if they exist.

Edit- Just calculated that a full 42 gallon tank is about 250 lbs...so I was short about 200 lbs gas, which means I had about 200 lbs extra in back including a full tank. The ride was just ridiculously bad, in any case.

An update on the situation: I just ordered a set of 4 Bilstein Heavy Duty Monotube shocks. From all of the selections below these seemed to be the best. It looked to me that reflex shocks are a relatively minor improvement over normal twin tubes, and monotubes are really a significantly different and better design. $260 shipped from shox.com for all 4 (these guys are pretty good, shipped same day at 4:30 PM and I'm getting it next day in orange county :)). We'll see how they work. Will post an update when they get installed tomorrow.