Precision 18, but the 4' headroom is a bust (its a shoal keel/centerboard combo). Good luck finding one for under $4k, but in this market, its "possible."
The Capri 18 is a better boat, but heavier, and deeper draft (26"). Cockpit is 6'8" on the capri, I think 6'4" on the precision (both production boats that have decent resale as they are still made and parts are readily available). On the precision there is a keel though... so it's not much different then the 192 in that regard.
The 192, is probably your compromise boat, but it's resale is likely less than a precision.
This is a better question for the trailersailor board...
Was thinking catalina 22, yeah big, but even with the swing keel it still sits below the bottom of the hull. Frankly I can't think of any design that leaves you with a round bottomed sailboat. Centerboards do, but you are looking for a cruiser.