Having owned only one hot tub I can only speak of my experience with that. We have had a Hot Springs Grandee for 18 years. It ran perfectly for over ten years when an aftermarket ozonator went out. A few years ago the heater gave out. That's it. The shell and the motors have held up without any problems. That kind of reliability is hard to find.
Going Hot Springs, 6 person, and a gazebo for $10-12K? That's going to be hard to do. Maybe you want to focus on buying a good tub for now and doing the gazebo later. We were going to build a gazebo after we put the tub in but one night, while looking up at the stars, we realized we'd lose that view. And in the winter, when it's clear and cold, the stars really shine. We decided against the gazebo and I'm glad we did.
Something else you may want to consider is a concrete pad for your tub. We dug out the hole ourselves, framed it, installed drain tile, trucked in gravel and got a concrete truck to pull into our back yard and finished it all ourselves. Today that pad is still as level as the day we poured it. It was a lot of work but it was worth it.
Another thing to consider is the electric. You will need space in your panel (ours required a 2-pole 50 amp breaker). You will have to run wire (conduit is required here) and, at least for ours, an outside breaker box. I'm an electrician so I was able to do all that myself but if you can't do it yourself, you'll have to figure the cost of having it done. Depending on the tub's electrical requirements, codes, the distance to the tub and whether or not you'll need additional panel space inside the house, the costs could add up.
