Those look like cool products, but I think that they'd be pretty expensive. That's not to say that Acard SCSI to IDE adapters are cheap, but these look much fancier.
If you get a 50 pin to 68 pin adapter and a short cable with a 68 pin terminator, you can get an AEC 7726H or 7726Q for less than $50. I bought a bunch for about that price and would even sell a few for $40 USD, if anyone is interested. I have a Quadra 700 set up with an IDE drive and a 7726H and it fits nicely.
Another option is to get an Acard 50 pin SCSI to SATA 2.5" adapter and put a 2.5" SATA SSD drive in it. SATA SSD drives are getting pretty cheap, but the Acard SCSI to SATA is pretty expensive. On the other hand, it'll fit anywhere that any 50 pin SCSI drive will fit, including the Quadra 605 type cases.
If you get a 50 pin to 68 pin adapter and a short cable with a 68 pin terminator, you can get an AEC 7726H or 7726Q for less than $50. I bought a bunch for about that price and would even sell a few for $40 USD, if anyone is interested. I have a Quadra 700 set up with an IDE drive and a 7726H and it fits nicely.
Another option is to get an Acard 50 pin SCSI to SATA 2.5" adapter and put a 2.5" SATA SSD drive in it. SATA SSD drives are getting pretty cheap, but the Acard SCSI to SATA is pretty expensive. On the other hand, it'll fit anywhere that any 50 pin SCSI drive will fit, including the Quadra 605 type cases.