Connecting External CD-Recorder

I'm going to connect an external Plextor 8/2/20 to a powertower pro 225 which has a 3940uw inside. I am using the internal fastbus for the boot drive and an individual port off the 3940uw to each of my (2) 9.1gig drives for audio, which I currently have mounted internally. The question is which is the best port to use to connect this etternal cd-burner? I have considered using one of the external connectors on the 3940uw but fear it might compromise the performance of the fast hard drives, since it is a 50 pin. Connection-wise it appears the SCSI connector on the back of the machine would be the easiest, but that goes to the computers internal slow bus I believe. Any help would be appreciated.
Thank You.