I have been using Bytecc external enclosures, one for my Maxtor hard drive and one for my Lite On DVD-ROM drive, they work perfectly. You can find them at Dealsonic.com. They have the lastest chipset and will allow you to put in a hard drive greater than 137GB.
I currently have a Maxtor 120GB 8MB cache in the external enclosure hooked up via firewire, it also has USB 2.0. Transfer rate is super fast and no problems whatso ever. Altough I am running out of room and I just purchased a dual firewire enclosure planning on putting in 2 Maxtor 160 GB drive in it. If you are interested in buying my Maxtor 120GB in the external case, please email me at firstname.lastname@example.org