It may be that there's no ACA500's at the moment because I believe Jens working on a revision 2? Which he mentioned over at EAB http://eab.abime.net/showpost.php?p=...postcount=1504 which sounds like a good upgrade for yourself unless your thinking of getting other Amiga's like A1200?
And there's Amibay for some community trading http://www.amibay.com/forum.php and you could check out http://eab.abime.net/index.php there is a member on there "kipper2k" whose always developing for the Amiga like a new Gotek. Also there are others that are doing things for the Amiga.