If the only reason you've held off buying a Zune is the 30gb hard drive and your lust for more and more space, then you're a shallow human being and should be roundly thrashed. Still, since it's almost Christmas and I'm of a generous bent, I'll instead point you in the direction of the good folks at Zune Scene. Yeah, they've taken their lovely Zune, still cavorting in its Microsoft warranty, and they've opened up its virginal chassis and swapped out the storage for an 80gb model.
Now, instead of 7000 tracks or a paltry 25 movies, you can store 70 full-length movies and almost 20,000 tracks. All of a sudden the subscription-based Zune Pass starts making a whole lot of sense, as buying each track individually would get very, very expensive!
The only downside is the removal of some metal shielding to accommodate the slightly thicker drive. Zune Scene are careful to point out that doing so might make your DAP slightly less resilient to drops or being trodden on, but if you're that slapdash with your electronics you should maybe stick to a xylophone anyway.
80gb Zune Review [Zune Scene]