first of all congrats on the amp. good move uv removed the sub. its the problem and now ur sure of it.
what kind of sub u buy next is entirely upto u.
what kind of music do u want to listen to
and what is your budget for the sub.
my suggestion is still the jbl p1222 mated to this amp. it'll be a perfect match as to what u said u wanted from ur setup. sell the cv and save up for the jbl