There's a Hitachi 160GB 2.5" drive on newegg already. And various other flavours of drive over 60GB (80/100/120).
I'm perhaps as interested in taking a 3.5" drive, putting it in an enclosure, and using a 3.5" to 2.5" adaptor, if that is possible. I'm assuming you can't just use an external USB HDD as the "main" HDD (I assume something has to be connected in the 2.5" port to act as the primary HDD for caching etc. whereas a USB connected one would just be read as mass storage for things like media files etc.).
I'm perhaps as interested in taking a 3.5" drive, putting it in an enclosure, and using a 3.5" to 2.5" adaptor, if that is possible. I'm assuming you can't just use an external USB HDD as the "main" HDD (I assume something has to be connected in the 2.5" port to act as the primary HDD for caching etc. whereas a USB connected one would just be read as mass storage for things like media files etc.).