Critical Damage bonus and Critical SPELL Damage Bonus

So, i have Maligaro's Virtuosity Fine Bracers and my CDB is 300% and won't go further.
I know it's useless to add CDB stats cause with gloves it's capped on 300% but is it the same with Crtitical SPELL Damage bonus? Is it stacking on classic CDB or is it a different stat?

Nope, you'll still be at 300% for any ability.