thought i don't have experience with that particular guitar, i bet the two output jacks are for the piezo and mag pickups and you can probably select between having both the piezo and the mag come out of one or have them in stereo(use both jacks) or just use the mag by itself.....i seriously doubt you'll need extra gear for it unless you really want an extra amp to take advantage of the strereo guitar.

as far as quality goes, i doubt you'll see a difference between the 7 and 6 string models. music man is pretty consistant with its quality so i doubt there's a difference...just would you rather get a 7 string or a 6 string.