I need help determining if I should be using multisite, buddypress, or both.

The plan is to have a site where musicians can pay to have a presence on the site where they can upload pix, bio’s, vids, and mp3 files. Free members can stream the mp3’s and rate them with the highest ratings showing in the chart on the front page. Members can also purchase music and/or schwag from each of the bands. I’m thinking that I need to use marketpress along with multisite to give each band their own “store”, but wouldn’t that compartmentalize each band site preventing users from browsing bands, etc? If not I may not need buddypress. I’m new here from the Drupal world…how far off am I?

Thank you