The matter of the sufficiency of the Bible's teaching for salvation aside, should Sola Scriptura be defined:
The Bible is the sole infallible (and the final) authority on faith and morals...
OR
The Bible is the sole authority on faith and morals... ?
Do you think that there is a significant difference between the two?

I would be perfectly comfortable with saying that the Bible is inerrant, infallible, the final authority, etc., on everything which it touches upon, everything that it says. I used 'on faith and morals' not to limit the Bible's authority, but just because the things of faith and morals are generally considered to be, in general, the things about which God is telling us through the Holy Writ. They are broad categories under which any Bible subject/topic you want to bring to the table fall.
I'm much more concerned about the existence of fallible, error-prone, non-final authorities on those matters which the Bible speaks of, which the former definition provided seems to be open to and the latter definition seems to reject, instead taking a 'Just me and my Bible' approach. I'm thinking mainly of the writings of the Church Fathers, creeds, councils, confessions of faith, expert Bible teachers, etc., as having some authority in the Church (although in no way on the same level as Scripture, the only infallible, inerrant, final authority -- this must always be crystal clear). It is the difference, some say, between Sola Scriptura as historically understood (by the Reformers) and 'Solo' Scriptura (a much later, 'revisionist' phenomenon).
See here:
http://www.the-highway.com/Sola_Scriptura_Mathison.html