SCSI support in OS X truly sucks. I've never got it anything other than the internal SCSI on a PowerMac (and at times that's fought back) working.

I bought (at no insignificant cost) an ACARD SCSI card for my B&W that is supposedly OS X certified. it works but doesn't boot OS X (boots OS 9 just dandy). I have a 2940, dunno if that works. I at once stage imported a ATTO card similar to yours from OWC and that didn't work in OS X at all. I had to send it back to the USA for a refund.

I pretty much wrote off any chance of getting bootable SCSI and OS X at any decent speed.