After reading recommendations on this site, I recently bought a "Seagate 500GB FreeAgent USB 2.0 7200RPM External Hard Drive" from Buy.com for $123.49, which included free shipping.
So far, everything is working well. I have recorded many children's movies on my 622 and archived them to the Seagate, in anticipation of the arrival of the grandchildren at Christmas.
I also put a couple of Seagate SATA drives in my computer 1.5 years ago, and they have been great. So I would recommend that you at least consider getting a Seagate drive for your 722.
Richard