Take my opinion for what's worth, I'm just another fool on the internet...
But, I have been serviceing spas for about 10 years. I am Independent service company. I do not sell spas, so I have no loyalty to any brand per say.
Cal spas are average quality at best. They use they same balboa controls as 80% of they spas out there. I can tell you I have seen a few new shells cracking around the led lights... And quite a few leakers that were brand new.
I don't feel that their customer service is all that great either. Costco can't help you there, where a dealer could.
Go try a sundance, jacuzzi, d1, marq... what ever.
Look around, wet test, and ask questions... Find a dealer who will stand behind what he sells. 5-6 grand is alot of money these days!
I'm not bashing Costco either, I feel that spas are kind of a specialty items that need a dealer with qualified people to handle any issues you might have.