That would put a fair number of KitFoxs, Avids, Rans's, Kolbs, Ridge Raiders, X- Airs, Flightstars and a host of others in the picture. A lot depends on how far you are willing to travel to pick one up. It also puts a lot of T-crafts, Aeroncas and Luscombes in the equation too. It's still a buyers market right now with prices very depressed. Have cash in hand and keep looking and a good deal will show up.
The Challenger is still an option. You can install the 3rd door option and there are aftermarket larger fuel tanks to extend the range if you feel you need it. If you have your PPL, you can put an in=flight adjustable prop on the 582 and really improve the overall performance of the plane. All that can be done as you get the cash later. In the mean time, you are still flying.

I've seen lots of decent Kitfox and Avids in the 15K range. 90MPH cruise in one is much more realistic than in a Challenger. I'd much rather fly in an all welded Chromoly fuse than a metal can. I just did a run through Barnstormers and theres a Kitfox II for $14K. There's some good reading on the Kitfox website here http://www.kitfoxaircraft.com/KitfoxHistory.htm if you want to learn the history and the differences between the I, II, III, and IV models. A model IV with a 912 would be ideal but they are running high 20's and into the 30's right now. Avids tend to run a bit cheaper but are basically the same exact airplane especially the earlier models. The parts are all interchangeable. Good luck in your quest. Not sure how familiar you are with Barnstormers but the way I search is Browse Ads and then click Experimental on the left side. That shows all the experimentals. I surf it every couple of days just to see what's out there and what the market is doing.

For your situation, I think a STOL enhanced J3 Cub, Avid, Kitfox or Just Air Escapade would do a good job and is woth spending a few additional $$ for.

Flew in one of these in Hawaii recently: http://alaskaslist.com/1/posts/10_Trans ... Trike.html
Pretty damn cool and cheap.