Hips,
You should consider a few others before you decide.

Acat - single handed, high end, high cost, lots of racing, high level of competition, box rule so you can tweak and change your boat within the 7 rules, boats hold their value well, lots of used boats for less money, $6k for a used older boat, to $25k for a new all carbon min weight. Unirigged, easily rigged, lightweight, easy to move around on the beach. www.usaca.org

F18 - Quickly becoming the 2 man class for racing, multiple manufactures (Hobie, Nacra, etc) tighter ruleset, lots of high caliber racing. New boats in the $16k - $18k range. http://www.f18-international.org/

N20 - Lots of nice boats for sale, used to be the defacto 2 man racer, being taken over by the F18. Lots of good used boats around. Check the classifieds on this website. $7k - $10k used. Lots of the distance races still done on the N20 including the Tybee500. http://www.tybee500.com/