Yes, Quadra uses 50-pin SCSI. Adapters mentioned by me are nuBus cards - Quadra 610 probably needs NuBus adapter to use them (unless you already have it inside Quadra). With either of these cards you'll achieve about 2x performance compared to builtin SCSI and you'll be able to connect newer, faster, quiter disks. These cards you can buy for instance here:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=160143538011