The Sirius S50 is the first, and for now, the only portable player that lets you listen to Sirius Satellite radio programming—sort of. It plays live channels only when connected to the Car Kit or Home Kit dock; when used as a portable, it relies on songs and radio programs recorded in its 1GB of internal flash memory. It's a limitation you learn to live with. If you're a Sirius subscriber and want to tote your tunes, the S50 is the way to do it.

The very compact 6.5-ounce S50 isn't iPod-nano small, but at 3.9 by 1.9 by 0.7 inches, it slips easily into a jeans pocket. The button-free glossy black face collects fingerprints but otherwise looks great. The bright, 176- by 220-pixel color display shows channel and track info that includes artist, title, and duration. The volume control and hold button are on the left side, and the Power, Menu, and track navigation controls are along the right.

Every S50 ships with a Car Kit containing a dashboard-mounting system and an antenna. The vast majority of satellite radio subscribers listen primarily in their cars, so bundling the kit makes sense. A built-in FM transmitter sends the Sirius signal directly to your car stereo. You can connect the player to your home stereo using the Car Kit, but the $119.95 Home Dock makes a more attractive living room component. The Car Kit and Home Kit each come with remotes for changing channels.

Before you can enjoy the S50 portably, you need to prerecord programming. You can capture blocks of content that are as short as 15 minutes or as long as 2 hours. You can also set the player so that it simply captures programming when docked.

But the infinitely more compelling way to load your player is one song at a time. Whenever you hear a song that grabs your ear—perhaps that great new Bloc Party track—you can just click the "Love" button using the dial, and the player grabs the tune. And since the S50 caches the first minute or two of every song, you don't have to catch the content you want right at the beginning. You can sort by artist, title, or genre. This is a great way to build a library of favorites, one click at a time. Just keep in mind that you can't move recorded files, which are copy protected, onto other devices.

The included earplugs are very bulky and, frankly, hurt my ears. As you'd expect from a severely compressed 96-Kbps audio stream, the sound isn't particularly loud or clear either. I also tried a set of Etymotic ER6i headphones, but even with those the audio sounded flat and had weak bass. Still, even though you don't get CD quality, the sound is better than from FM radio. The player did sound much better when hooked up to our home stereo. Unfortunately, you'll find no bass or treble controls.

Recording tracks is a cinch—but finding them afterward can be a bit tricky. The menu system is particularly nonintuitive. The Power button brings up playlists, but you have to use the Menu button to find your preprogrammed content. Neither is helpfully labeled. Although voice prompts told me what channel or menu option I was viewing, this was cold comfort as I tried to figure out the device's byzantine interface.

The S50 also lets you move your own WMA and MP3 files onto the player from your PC via the included USB 2.0 cable. To do so, you have to load the proprietary Sirius software. The S50 is also plug-and-play- compatible. You can fill just half the player's 1GB capacity with your digital music files, which is pretty stingy (the rest is reserved for Sirius content). If all you want to do is play MP3s, you'll find cheaper, more flexible players out there, such as the