Hi Eric,
SP Ultra 5's are Stillpoints Ultra 5 footers. There are also the Stillpoints Ultra SS footers. The Ultra 5 are their top of the line (bigger and more expensive) but both are extremely effective at what they do. I use both in my system (but not under my speakers).
Also, since you enjoy your system so much for movies - if you haven't heard of Screen Innovations - you should check them out. They are an Austin based company that makes video projection screens. The Screen Innovations Black Diamond projection screen is the best projection screen that I have ever seen. It is pretty amazing.
Arnie