If those speakers were $16,000 new and they are 13 years old, you should ask $8000. The shipping on a 275 LB speaker will cost a small fortune so you should list them with local pickup!
http://www.enjoythemusic.com/magazine/equipment/0802/bwnautilus800.htm
http://www.enjoythemusic.com/magazine/equipment/0802/bwnautilus800.htm