I would also vote for no Heki. The light and ventilation are great, but it is poorly executed from non-sunlight resistant plastics and quite fragile. If you later change your mind, there is no replacement that will fit the hole, so it is a forever decision.
If you do get the Heki, store it out of the sun or make a cloth or wood cover to keep the sun off of it. That done and treated very carefully, it would last awhile. Also consider having them install the crank up version, which does not require opening the bug screen (and letting in all the bugs) when you want to adjust the dome opening. I have not had issues with too much heat coming in most of the time, also living in Northern California. If you spent a lot of time in the south or southwest that would be more of a consideration.
