I went from Monroe SensaTrac shocks to RCD Bilsteins to single adjustable QA1 shocks on the rear of my '73 A-body.
The Bilsteins were a noticable upgrade and improvement in suspension control, and pretty much spot-on for a classic performance car.
The adjustable QA1 shocks were another step up in control and handling. Being able to adjust the rebound of the shock has been very welcome on my setup.

I went from KYB's on the front to single adjustable Hotchkis shocks. Same deal. Very noticable upgrade.

With a Hellwig swaybar on the front and after the shock-upgrades, the car was a great deal more stable and felt 'glued' to the road, without the typical 'vintage' soft handling of older cars.