The Napster subscription service introduced a new pricing tier that allows users to stream an unlimited number of songs and download five DRM-free tracks a month for $5. The offer does not require subscribers to download the Napster client, but rather can be streamed from any Internet-connected device, such as computers and WiFi stereos and receivers.

In addition, the company will sell prepaid cards redeemable for the monthly service in Best Buy stores. Best Buy acquired the Napster service last October. Napster COO Christopher Allen said Best Buy employees will also try to upsell customers who purchase Internet-connected devices on the new Napster plan.

The move is aimed at challenging iTunes, specifically by not challenging the iPod. Because all music downloaded from Napster (free or otherwise) is now iPod compatible, Napster no longer needs to make the “iPod is too expensive to fill with music” argument. Instead, it’s going after the 30-second streaming samples that iTunes users are limited to. For $5 a month, Napster users get five downloads (which is the same cost as buying five songs from iTunes) AND unlimited full song streaming AND iPod compatibility.

Napster will still retain the Napster To Go portable subscription for $15 a month, which relies on Windows DRM devices, but clearly the emphasis is on this new offer. Allen says there will be no advertising on the streaming music service.

The news comes just as the Napster brand is set to celebrate its 10th anniversary. See Billboard’s full interview transcript with Allen to learn more about this new offer and the company’s thoughts on this milestone.