Migrating from SQL express 2008 to 2012 enterprise

I've got a few sharepoint databases that were configured with RBS. They are currently on 2008 Express. 

The database size is about 10GB with another 10GB in the RBS location. 

I need to migrate these sites to sharepoint 2013/SQL2012 enterprise. 

I understand the process (both sharepoint and SQL). i.e. turn off RBS, migrate all data back into the database, backup, restore, attach to sharepoint 2013. 

This works fine for smaller databases, but because they are on SQL express there is a DB size limit of about 10 GB. 

When I run the $rbs.Migrate() command to move data back into the database it fails because it hits the size limit in express. 

Is there a way to move SQL DB's and RBS files without merging them first?

Thanks!