I can't speak for the Sprint or CTX but the STS only has one MOH channel, so if you need two seperate sources, the STS may be a non starter. If you are planning on doing much recording and setting up two different Auto Attendants, I would stay away from the inskin VM for the STS and look at the digital dispatch. They do have a new hard drive version of the inskin, it may have more flexibility than the original inskin version, someone else may chime in on those. As far as reliability, we've put in apx 15 to 20 STS's and apx 100 sets, the oldest almost two years ago with one out of box failure of the KSU and no phone set problems to date.