I'm very happy with my EZQuest Boa 120GB. Generally, just follow the guideline Digi says (7200rpm, oxford 911 chipset, seek time, etc....). And I really like that the EZQuest has an internal power supply, vs. a wall wart.
I highly recommend the drives at Other World Computing (macsales.com). They meet all of Digi's requirements, and mine has worked flawlessly for about a year now with my iBook 700 with both an Mbox and 002r. Also, their prices are as good as it gets. Another way that might be cheaper is to get an external firewire case (with the Oxford 911 chipset) on Ebay and use your own 7200 rpm drive.
----------------------------------- A word of Internet Forum wisdom: Disregard any advice that begins with "I've heard..." 97 M3/4 - S54, TRM Coilovers, UUC SSK/Sways/LTW Flywheel