It's important to play 6 & 7 course for the renaissance repertory. I understand the issues of resale value, etc, but I really think for most of the 16th century the three instruments, 6 course, 7 course _F and 7 course D give the most insights into the music.
Also, if you are going to sell the lute it is best not to buy it :) As important as course, ideally one should have an instrument set up for intabs and one for ricercars, and the optimum setup really requires the right number of courses. It's possible that without the best setup, it might be harder to learn certain techniques, and that an eight course could become a bit of a tugboat. There's a big difference in the sound when the eighth course goes on, which is immediately attractive, but for me, ultimately, later sounding, rich rather than clear. Many instruments share these issues of practicality and range. When buying an Italian harpsichorp, people have to decide whether to buy an instrument with a very wide range, so they can play "everything", or an historical instrument. But there is a fundamental difference in the sound; sound vs practicality: no easy answers. dt To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
