As always, it depends on what kind of sailing you want to do and what your local fleet does.
The M4.3 or N4.5 are just too small for your local waters. The short chop of the Gulf of Mexico will make you hobbie-horse and beat you up. Catman had it right with a GCat 5.0. The Supercats 15 or 17 are excellent for your Clearwater Intercoastal and Gulf recreational sailing. If you want to race buoys at Gulfport, board boats are OK. However, if you want to rec sail at Dunedin (island hop, steeplechase-type distance races, beer on board, sunny days with a local beach Betty on the wire) then look at what the locals sail...boardless or swing centerboards. Super 15? We have one! SC17? Several. GCat 5.0? Sure, Hans built them all and will kick your butt on one any day you like. Dart 18? LOTS here and a good boat all around. Your P18 was a GREAT boat but if smaller is needed, a P16 is hard to top. Want to sail with the BigDogs? A Tornado has swing boards, no? And Robbie could fix you right up.
But the BEST boat is my Mystere 5.0XL which just might be available...see your PM. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />