I have a Buz Card for Mac, and use it in pretty much the same way as you, as an offline to cut on and master to a Media 100 with EDL.(posted 9138 days ago)The Buz card is capable of maintaining the sync, as long as you use the latest version of Premiere to edit with (v. 5.0). It was Premiere's fault that sync drift existed pre 5.0 due to a time base of 30fps and not 29.97fps.
I've found that as long as your drives can handle the data rate, and using the onboard UltraSCSI from the Buz to an Ultra SCSI drive is the best way to achieve this. But even at low quality (25%), I can digitize to my internal HD without dropping frames.
NOTE: If you plan to use Premiere to edit with. and need a frame accurate EDL to take to an online session, then when you digitize, make sure your preferences specify you want the digitize to abort on dropped frames. This will ensure that any TC based EDLs use clips whose TC is frame accurate.
Best O'luck.
Da