It looks like my search for a functional Serial ATA enclosure that supports Spread Spectrum Clocking enabled drives has finally paid off. After contacting numerous manufacturers and distributors and even an email to Oxford Semiconductor themselves, I've stumbled across an enclosure which does in fact support SSC SATA drives.
Despite the fact that several of my emails went unanswered, and that no manufacturer would admit to making an enclosure that supported SSC, it turns out that CoolGear does in fact make such a beast.
I played a hunch, and ordered this puppy from CoolDrives.com, also available from SATAGear.com. I've only had a short time to test it out, but so far it's two thumbs up. Stay tuned for a full review.