From what it sounds like, you are already scoring fairly well on your practice tests.
If I were in your shoes I would want to know what the course covers. Most crash courses try to cover all aspects of the test, and give you an idea of everything, but don't go in depth into anything. If you already understand the test format, and have a good grasp on many concepts, you might be light years ahead of the average student in that class. This class might also be geared towards the person that needs a 550 or 600 to get into their program, and doesn't want to dedicate months to studying. It might serve you better to drill down on the concepts that you believe you can work on, or purchase packages from companies that will offer specific problems, material, videos, etc directed exactly at what you need.
If you are going to spend the money, there are most likely better options to help you with the remaining concepts you need to know to break that 700 barrier. PS, with one month to go, I would book your test day, and start working towards the finish line. You are close, and 3-4 weeks could be enough to get you there with some well calculated studying. You just don't want to get stuck with a crappy test time or day of the week.