hydro spa millenium i buy it in 2000. control boxs p/n53431 model hsexp3 model DE-HSEXP3-ECAH DE-HSEXP3-FCAH pat.no 4618797 i 1 pump 2speed 2pump.-2speed 1 and 2 are 5hp. I'm needing a new control box for my spa. So the question is, can I use the GL 2000 on my old spa, or do I need to switch out more than the control box (heater). Regards John A. Rodseth [email protected]