RE: CTS - If you've got that much experience you shouldn't have too much trouble with the CTS test, however, you could get hung up on some of the project management lingo that they use. The test study guide will give you what you need. See link here
As stated by axp27, Dante certification is also very helpful. If you're looking to work with an integrator, they'll be certified dealers that will enable you to do manufacturers certifications
Most of the questions are from the book anyway rather than from the available classes.