Not only does Sony Connect sell their DRM songs with the weird ATRAC3 format, but I can't access the site using Firefox, here's the message I received:
We appreciate your interest in the Connect music store, but our store currently only works with Internet Explorer 5.5 and above. You don't seem to be using that particular browser at the moment, so, unfortunately, we'll have to part ways until we support the browser you're currently using or you upgrade to the latest version of Internet Explorer.
So you don't have to download a specific software application like iTunes, but you do have to have specific software (Internet Explorer) to access the site. Furthermore, nothing in the language above seems to point to the fact that they seem to be making any effort to make their site compatible with Mozilla.