It is my belief too that the SCSI card was the only XCI board which actually shipped. Other boards were announced but do not seem to exist in the wild.
InfoWorld
January 16, 1989
Daystar to Offer 33-MHz SE Accelerator
BY ROBERT SNOWDON JONES
...
Daystar will also introduce three enhancement boards for the Mac II based on its Extended CPU Interface (XCI), which bypasses the 10-MHz limitation on the Mac II's Nubus. The boards plug into the Nubus slot but have a connector that gives them direct access to the CPU. The Video XCI gives higher performance graphics capabilities and is compatible with EGA monitors in addition to the Apple 13-inch monitor and the Sony 19-inch monitor. The Daystar HD XCI uses cache memory to increase performance of hard disk drives.
Andrew Lewis, Daystar's president, said the company will place XCI in the public domain in hopes of spurring more high-speed hardware for the machine. The Mac II's current speed limitations hamper its usage as a CAD or graphics workstation, he said.
XCI is a connector with a few chips, which bypasses the 10-MHz limitation on Apple's Nubus slots. The interface permits a direct 33-MHz path to RAM, video, and disk drives.