I found this page, which indicates the current firmware revisions and confirms that 400i is the latest for this drive.
I guess that answers my question. I wish this had been easier to find.
This message was posted on behalf of Intel Corporation
As you found out, the latest firmware version for your SSD is the latest one. The link you provided is the correct in order to verify each SSD series.
We are glad you found the information and in case you have further questions please let us know.