I plan to eventually add a "weekend" car as well - focused on a cabrio. Top of the list has been a 911, but the reviews of the 2013 Boxster S sound interesting. Have also considered the M3 convertable. never been a big fan of the SLs.
Current: 2013 Monte Carlo Blue F10 M5 (ED on 9/1/12)
Previous: 2009 Carbon Black E60 M5, 2006 Silverstone II E60 M5, 2003 Sterling Grey E39 M5, 2000 Anthracite E39 540i6, 1998 Jeep Grand Cherokee 5.9 Limited, 1990 Eagle Talon TSi AWD, 1978 Mazda RX-7