The wife wants the clean look of an electric range so I guess I'm not only
going to have to run a 220v 50A circuit for the range, but also install a
sub-panel because I was down to 2 open circuits in my present 100A service
box.

My first inclination is to install a 60A sub panel because I will of course
be installing at least one 50A circuit. Yet, a 60A panel with one 50A seems
like I'm cutting it close.

Also my intension was to use 6/3 for the range circuit (about 25 feet long),
what should I use to run to the sub panel. The run won't be more than 2 feet
(I'll be mounting the sub panel about 8 inches from the main and connecting
them with EMT). I would think it would also be 6/3 because that's rated for
65A.