I'm in love with the Creative Xmod. It's this little white box that hooks up to your computer by USB. And it turns your plain ordinary headphones into a virtual 5.1 surround sound system. I used it to watch my copy of Cars. I tell you, those race cars were racing around and through my head. That's how cool the virtual localization was.
The box works by creating virtual speakers that surround your ears. Yeah sure, your headphones only have two real speakers, but somehow the engineers at Creative have figured out how to localize sounds by using advanced digital signal processing that even takes the physics of your head and the shape of your ears into account. It wasn't exactly like being in a theater and really feeling the sound effects with your whole body, but it took the sound experience up to a whole new level of listening.
The XMod hooks right into your Mac via USB. It then grabs any audio playing through the system and runs it through its built-in filters. You hook up a pair of earphones or speakers to experience the effects. The virtual 3D surround sound works particularly well with both movie playback and gaming.
There are two output jacks on the unit. One for headphones, one for speakers. That's because the physics of headphone playback seem to differ from the physics of speaker playback. With headphones, each ear hears a separate and distinct signal. With speakers, there's no head stuck in the middle and there are cross-over sounds because your ears can hear both outputs, so the virtualizer has to take that into account.
In addition to the virtual CMSS-3D speakers, the XMod also offers a Crystalizer feature. The Crystalizer restores a good deal of the dynamic range that gets squeezed out during MP3 compression. It produces deeper bass sounds and clearer voices, providing a clearer, better defined signal for playback. This worked great with compressed, clean audio, like the compressed WMA signal from my Zune. (I know, you're cringing to read that. But it really made a huge listening improvement.) It worked less great with "home audio". I listened to several rough and noisy podcasts and the Crystalizer just enhanced the worst bits of the noise. So you'll want to pick the right times to switch this bit on. You can enable and disable both the 3D and Crystalizer features via switches at the side of the Xmod unit.
If you want to step up your Mac audio to the next level, but you don't want to spend a lot of money on sound cards and speakers, the Creative XMod is a great way to get a lot of bang (and crash and boom and kapow) for your buck.