There is no CS-MARS replacement product offered by Cisco directly. They left that market segment when they killed MARS off. What they do instead is publish a list of "Technology Partners" that offer SIEM solutions recommended for use in Cisco environments.
The design guides for the partner products are posted in Cisco's "Design Zone" portion of their site, found here:
One of the linked documents linked, the "Lippis Report", explains the philosophy they've adopted now.
The program's "Cisco Developer Network" section also includes additional information on each of the partner products.
For reference, these are the 6 recommended partners/products:
There are other options that aren't mentioned here, but this would be a decent place to start.
Message was edited by: Michael Crowe (better CDN link)