Have you seen that Sirius commercial how it's one step ahead? Im not sure it holds that much MP3's if any. Actually, heres some details:

Sirius Stiletto vs Ipod Touch
-True Portability. The Sirius Stiletto will have a built-in antenna that allows reception of Sirius' signal without the need for an external car-dock or home-dock.
-Antenna/headphones included. For supplemental reception, you get a Sirius antenna strapped to your noggin - included with the Stiletto.
-100 hours of Storage. The Sirius Stiletto handles MP3/WMA, and allows you to intermingle Sirius content with your own digital music collection. The Stiletto supports Microsoft's PlaysForSure protocol.
-WiFi Capability. The interface (pictured to your right) looks very similar to the Zing interface as SBS points out. I'd it's not too far of a guess to say that the Stiletto is using the Zing's WiFi technology - allowing you to stream Sirius online when you're in a hotspot.
-Battery Life. Two batteries are included with the packaging. One standard, and one extended life, which offers 4 hours of live SIRIUS reception, 14 hours of WiFi reception, and 22 hours of stored playback time. (The wording is a little fuzzy here - are these numbers from the standard battery? extended battery? or both?)
-Cost. The Sirius Stiletto will MSRP for $399.99.
Hmm...probably not enough to scare the iPod family.