My suggestions are probably different than those that most others will offer.
I'd suggest you consider a USB3/SATA docking station, such as:
http://www.amazon.com/dp/B00APP6694...=2025&creative=165953&creativeASIN=B00APP6694
or
http://www.amazon.com/Plugable-Dock...=2025&creative=165953&creativeASIN=B003UI62AG
If you'd prefer an actual "enclosure", get this:
http://oyendigital.com/hard-drives/store/U32-M.html
Then combine with a "bare" hard drive or SSD drive of your choice. For audio projects, an SSD could probably take anything you could throw at it.
You might also consider partitioning an external drive, to create at least one or two "work partitions" that will be roughly 2x-3x the size of the projects you normally create. The advantage is that by "cordoning off" a partition of the drive, all your input is recorded to a small area of the drive's platters, reducing the time the drive has to spend "sweeping the surface" of the platters to find sectors to which to write. It also makes it easy to defrag the work partitions, to keep large blocks of free space available.
That's what I do, works fine for me...