Here is my report...
I got the 5.25" USB1.1 + Firewire enclosure ($69.99), also got some of the 5.25" removable hard drive enclosures (for 3.5" drives, $7.50). I also got one of the IBM Cardbus firewire cards ($26).
The good news:
-- The $7.50 removable ATA100 hard drive enclosures that geeks sells DO FIT in the external firewire enclosure! Tight, but good.
-- The firewire card from IBM was plug and play, built in drivers for both my Windows 2000 and Windows XP systems. Texas Instruments chipset.
-- The firewire mode of the drive enclosure itself worked fine with my IBM card, nothing special - plug and play.
The bad news:
-- The USB mode of the enclosure required the driver CD-ROM with both Windows 2000 and Windows XP. Not well suited to using to hookup to any old system.... I could not find the driver anywhere on the net, the only place it exists is on the CD-ROM that came with the system. GOOD NEWS: The driver worked with both Windows 2000 and Windows XP (just use the Windows 2000 one on XP, there was no specific one for XP).