For any kind of towing or performance interests, I would recommend checking for rust around your rear leaf spring shackles. It is possible, and relatively common in areas that salt the roads, for these areas to rust and push the springs through the rear floor.
Since you're not doing any towing, you'd be best advised not to get coilover shocks like the ones Monroe sells. These will give a very rough ride in the rear without towing weight. On the other hand, they will help level out worn leaf springs.
The shocks meant for handling and performance, such as KYB Gas-a-just, will give a stiffer ride and better cornering. It will be a bumpier ride on rough roads.
Economy shocks will be cheaper of course, but they may not control bounce as well and potentially wear out faster.
Your best bet on shocks for ride quality and handling balance will be something in the OEM replacement category, such as KYB GR-2/Excel-G.
Anything further than this and you'll want to look into other suspension issues and upgrades to improve ride quality to your tastes.