It looks like Alta has made a more powerful version of their bike, the Redshift MXR. It's supposed to have similar power to a 350 or slower 450. It's interesting that it has the WP AER fork on it. I wouldn't think KTM would want to share their latest tech with a competitor. Anyway, Dirt Rider has nothing but good things to say about the MXR and the improved MX models.
https://www.dirtrider.com/2018-alta-redshift-mxr-first-ride