I used mailcow with sogo and hated, it's so complicated, the HTML signature never worked, the images never loading, calendar never synced with apps and cross accounts, a completly mess.
Roundcube is easy, but this CrossBox really is nice solution, the price not help, I'm a small business with small private accounts but all they can get more from solutions like that, maybe a partnership between enhance and crossbox can offer a discount or something like that.