The Prism replaced the Gleam which had been around since 2014. Since it is technically a new model that has only been available since March, you are not going to find many reviews yet. Regarding energy usage, use the Caldera Cantabria for a guideline. It is basically the same hot tub but a Caldera in terms of pumps, insulation, efficiency, etc.
Envoy will fit 5 max with the captains chair. What is included in the prices you were quoted and what part of the country are you in?