The Monroe severe service shocks suck. (I had them in my '96 RMW.) The high-speed damping is too stiff (which means an uncomfortable ride and harshness going over bumps) and the low-speed damping is too soft (which means that the car wallows in turns and floats on the highway). The Bilsteins, on the other hand, are epic--comfortable ride AND good handling. (I have them in my '94 Caprice wagon.)
I run the Airlift 1000s in my wagon with stock springs all around. I leave them at ~5psi unloaded, and then air them up as needed when towing. If your stock rear springs are weak, get a new set and install them with the Airlift 1000s.
--'94 Caprice "SS" wagon, 0.30 over, high-volume oil pump, LT4 hot cam, 1.6:1 rockers, ported aluminum Corvette heads, shorty headers, PCM4Less tune, 4.10s, shift kit, side-exit dual exhaust with Flowmasters, OR X-pipe, F-body gauge cluster, Bonneville front and rear seats (working electrics), Bravada console shifter, Bilsteins, 12.7:1 Impala steering box, Boss 338s with 255/45R20s, bunch of other stuff I'm forgetting.
--'04 Mustang Cobra, '15 Audi S4
--1125R, 1050, VMax, VFR800, DRZ-400E