You need to give more details like what format are you working off and what kind of drives, how full they are, etc...
>The thing is it USED to play fine - seems like the bigger the project got (we're on version 10 now)
>the more problems I would have
I did work off USB 2 once, not by choice. By choice I'd go SAS/Fibre/eSATA and at the very least FW800, all RAID 5s, but the client gets what they want, and I won't pay for storage for a project if the client doesn't pay me for it. USB2 did perform pretty alright. I did encounter stuttering, but it was due to other issues (running off a laptop on battery, with an expanded internal drive).
Firewire is more consistent than USB. You may want to check your available space, and anything less than 15-20% is pushing it on a solitary hard drive.
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