Big thumbs up for Reus Audio, and in particular for Cliff and Kyle. The post-sale support has been head and shoulders above any reasonable expectation, and in fact has been better than Tesla's own post-sale service, and *that*, for the most part, has been somewhere between good and stellar with a couple of notable and glaring exceptions.
One thing that hasn't been noted upthread - they'll transfer whatever Reus system you currently have into your next Tesla for the cost of labor - figure about $2K. That means you've bought your last audio upgrade when you buy a Reus upgrade. Now, I have no idea what would happen if one switches from a Model S to a Model 3, but I imagine after they get their hands on a Model 3, all will be fine.
I configured my Model S with the base audio package, expecting to upgrade as above. The other day, I was in a loaner with the enhanced audio package. It wasn't bad - far from the Reus audio experience, but it had its good points and reminded me of the whole presales/demo process that I went through a little over a year ago. So when I get my next Model S, presuming that the extramural Tesla annoyances haven't driven me away completely, I will configure it (or buy a CPO) with the upgraded audio package, and then transfer the Reus components on top of that.
It should be noted that I didn't spend the money for extra volume or for thumping bass. I bought the Reus upgrades for accuracy and to get as close as I could to what I listen to at home. It was a successful venture, and has represented some of the best money I've ever spent for an aftermarket upgrade. And as you can see from my sig, I have a few of those.