Here is what worked best for me:
- I always use the same audio format MP3
- I host the audios on my site - upload them via FTP
- For payments, I use paypal.com and 2checkout.com
- For product delivery, I use Payloadz.com - customers receive a PDF file containing link, login and password to access their product page on my site
- I direct the customers to a password protected download page on my site where they can download or directly stream the audios one by one.
- They can as well download audio sets in zip files packages - 5-15 audios - 50-150 MB/zip file.
- Here is an example of how files are presented on my site: http://vitalcoaching.com/spiritualpower.htm#audios (This is a free product - Same for audios for sale)