I'm not sure if you've finalized your choice in SWG, but here is another one to consider:
The Hot Tub Wizard | Store | The Hot Tub Wizard. I have no direct experience with their controller. However, I've been using the Scepter replacement cells (same cell as in this package) for my Hot Spring Grandee, as it is plug and play with my factory ACE controller and they work extremely well! The Grandee is 500 gallons, and I had to dial this cell back some compared to the factory cell, so I have no doubts that it could keep up with an even bigger tub.