Personally I'd go for a 21-22" FDTrinitron/Diamondtron tube, whether from Sony, NEC/Mitsubishi or from another monitor manufacturer that uses their tubes. These are amazing. I'm using a 2nd hand hp p1120 now and it's really a lot better than the Nokia 445XPro 21" shadow mask that it replaced.
Just make sure that the dot clock is fast enough to support at least 1600x1200@85Hz though, preferably more. They mostly seem to top out at 1920x1440 or 2048x1536.
If you can't afford one new, I'd go for a 2nd hand one. HP, Dell and IBM all make nice OEM monitors based on the FDTrinitron tube
