For sound go as close to the front middle but back 2 rows. This is because of the angle off the speakers they "should" have setup.
For looks go as close as possible to the instrument you like to see. For me I like the stand up bass so I always try to sit as close to it as possible.
If you ever get a chance, and you have not seen them, go see the the Squirrel Nut Zippers. They are Ragtime jazz with a Vaudeville presentation. Awesome from just about anywhere in an 800 person or fewer venue.
http://snzippers.com/tour