I wouldnt be selling your music for you, I would be providing you with your own website which has the ability for users to listen to and buy your music directly. All sales would go straight into your paypal account (no cut taken).
the promotional aspect would be down to the owner of the site.

So the site owner would have the freedom to sell their tracks for as little or as much as they like and be able to create an indivdual brand for themselves while telling the user about themselves, news etc rather than just another name in a pile of thousands of others on sites like trackitdown.

You could of course use places like trackitdown to get your material distributed and use this as a kind of hq where people can get more info on you with the bonus of making more per sale.