Is it possible to upgrade from the basic Essentials version of X1 to Studio or Producer (X1)?

The only upgrade path at this time is to the X3 series. X1 Essentials does qualify for upgrade pricing to the X3 series.

Your only option for Producer, and the better option IMHO opinion, is to upgrade to SONAR X3 Producer. That's $399.
 
Alternatively you could also choose to upgrade to SONAR X3 Studio for $149 which has a lot of new content and all the workflow features we introduced across the entire series.