I ordered 4 of these:
Western Digital VelociRaptor 600GB
I have been waiting for this capacity for a while now now I can move my entire iTunes library (800GB) to my internal drive and now have more free space on my external for backing up (instead of running the iTunes library with no backup). Sure it's not as fast as an SSD, but I cannot afford 2.4TB in SSDs.
Great piece of kit, I have the 300GB VR and it's pretty snappy, if you check reviews most SSDs don't really blow it out of the water by much anyway.