@outlash does CX and has a C'Dale IIRC
There also a dedicated forum area for the discipline
Can you get a decent test ride on the bike to see if it's comfortable on the roads as presumably that'll be part of its use (as well as the muddy stuff)
I think C'Dales do indeed come up big for their designated size (due to how the sizing is determined) compared to some other brands, such as Cube, so that advice could well be correct. What do you have at the mo, and have you compared the geometries side by side? TT and stack are important measurements to compare