Rant received, the Colossus Prime and LF15X401 are pretty similar drivers, nothing lost there.
They're both very much sub drivers though and Cubo 15 focusses on 35-ish, although officially 40 Hz and up. The RCF will also work in Cubo Sub (will weight around 70 kg loaded) but will do that 30 Hz just as well as the CV does. Cubo 15 will weight unloaded about the same as the 18 mm sheet, you will cut it from, so a lot lighter but you might miss that lower oemphh...though it will be definitely just as loud as the CV, if not louder.
Best regards
Cubo