evening out your string volumes is not your amps problem, thats an issue somewhere else in your bass setup or technique.
As for the 4 PRO vs the CL I'd say they are pretty evenly matched - ie. one is not specifically better than the other, but may just be better FOR YOU than the other, depending on your needs... the difference is SS VS Tube
Have you played an all tube amp before? they have an awesome sound, but it's not for everybody, so I suggest trying one out before you make your final decision