I like Swirl Spa the best from what I've tried in Calgary:
http://www.swirlspa.com/
The ambience is a little more "healthy" then "luxury", since they share a business space with a yoga studio. But every treatment I've had there has been AWESOME.
FWIW, I personally find Stillwater to be overpriced and a bit overrated, but that's just my opinion. Lots of people love it.