That said, they were not an especially great light air boat and were not all that easy to sail to their rating on a either an upwind/downwind course or on a triangular course. Where they really came into their own was in distance races, which ended up being predominantly reaching races.
A boat that I would strongly endourse is the Soverel 33 which does great in almost all conditions. I would suggest that you try to find one of the Olson built Soverel 33's, with a Soverel built S33 as a fall back and the Tartan built boats as a desparation move.
Although slightly above your target rating range, I would suggest that you consider adding the Laser 28 to your list. Sailed well these were excellent light air boats that had an easy time sailing to their ratings in the light stuff. I owned one and really liked the boat but they are not everyone's cup of tea. I did find it pretty easy to catch the Olson 30's upwind and in light air. Around here, in light to moderate breezes the Laser 28 fleet would pass the typically catch the back of the Olson 30 fleet. In moderate conditions, they would pass us down wind and we would catch them upwind.
Another option might be the S-2 9.1. The S2 9.1's actually did much better in light air than their numbers would suggest. Be very careful to check for core rot since they had some of the worst out there, but many have been rebuilt and they remain a good PHRF boat.
As someone said above, masthead rigged, outboard engined J-29's do pretty well in light going and are good all-around PHRF boats.
That would be my thoughts,
Interesting. I used to think the same about the O-30 in light air, but there are a couple around here that have well proved otherwise, particularly in downwind drifters. That said, they are both very well sailed by folks who really know their boats. I'm wondering if the ones you're seeing are wet sailed... it does make a difference.
S-33, indeed! A great boat, especially the PBW version, with a lot of good information on their class website. Unfortunately it will be a much more expensive boat to run.
If one were going to do an older 30' ish racer/cruiser, the S2 is a nice boat and a good addition to the list, but for the money, I'd go with the Pacific Boat Works O-911s. The build quality of all the Santa Cruz made boats (Alsberg Bros (Express), Pacific Boatworks (Olson, Soveral), Santa Cruz) is tough to beat.
I can't think of a better 30' racer/cruiser than the O-911s that does both well and is still very competitive at it's rating. MH OB J-29 is a good boat as well.
A couple of lists:
Race only, Melges 24, Olson 30 or J-29 MHOB... S-33 if you can afford the sails.
Race/cruise, O-911s, S2 9.1, Santana 30/30, Capo 30.... most of these boats are probably beyond the OP's 20k budget.
... but a lot of good ideas and good choices to look at, that's for sure Jeff!