I'd definitely second the Careel 18. Good solid boat with an active class association. Always some demand too, which is something to consider when it's time to move on.
Red Witch - my father actually owned one of these about 30 years ago. Nice little boat - quicker than the Careel. They have a fairly low freeboard and cabin - part of their design was to be able to get under the bridges at Fremantle without having to lower the mast. Also an active association - as long as you're in Perth.
A quirk is that they've actually got a fixed keel, rather than a swing or daggerboard type. This frees up some room in the cabin, but means:
- They sit higher on the trailer;
- You need a deeper launching ramp;
- It's not as easy to tie up to the shore.
Anyway, check out
http://www.redwitch.asn.au for more info on them.
Other designs that come to mind:
The Investigator is quite a nice little boat. It has a swing keel that raises into a skeg so it doesn't intrude into the cabin.
The Austral 20 is a solid little boat with a good reputation. It says a lot about this and the Careel that they are still being made today, many years after the first ones were launched.
The Sonata 6 is fairly common boat. It has a class association that seems most active in Victoria - check out
www.sonatayacht.com .
The Clippers look a bit awkward to me, with that odd bow searching for a bowsprit. They carry their beam right back though, so they're probably fairly roomy for their size.
There's a stack of information available at The Trailer Sailer Place
www.communities.ninemsn.com.au/TrailerSailerPlace/homepage/msnw . The message boards there have a review of many designs that could interest you.
Good Luck!