And what are you going to use this boat for? You mention you want a cabin with full sitting headroom. Some of the really fast boats won't have that.
About the only rating common to most boats for comparison purposes has been PHRF, which seams to give some indication of performance but not much.
PHRF numbers are given time differences in seconds per mile with the base boat apparently being the 12-meters once used to race for the America's Cup (e.g. that's "0"). In other words, a boat that has a PHRF rating of 180 would be about 3 minutes per mile slower than a 12, on average. Of course, there are a lot of problems with single number rating systems like this - are we talking upwind, downwind, on a reach; strong wind, light wind, or nice moderate breeze. In addition, the system really doesn't work well at quantitative comparison across wide ranges. E.G. we know a 0-rater will be a lot faster than a 180-rater, but will it really be exactly 3 minutes per mile? The system works better for comparing boats that are more similar to each other.
SA/D doesn't seam to tell you much, as my current boat has a pretty good SA/D ratio, but is still pretty slow, even in light winds.
What do you define as a "good" SA/D ratio?
What you really want is a ratio of sail area to wetted surface area, unfortunatley few people really know the wetted surface area quantitatively. Qualitative comparisons are relatively easy, though.
But there are other factors besides just sail area, like rig height, that are also important.
Other than having an opportunity to sail on a bunch of different boats in different conditions, I think PHRF numbers are probably going to be the next best way to get a sense of the relative performance of a selection of boats. In other words, look for boats that meet your criteria: under 10K, fit on trailer, launchable without a hoist, cabin with sitting headroom, and then you can start to filter your list by PHRF....