Get the disc. Get the meter. Analog is fine. In fact Dr. Hsu recommends the analog over the digital. (Just be aware that you need to compensate with the analog at the lower frequencies but that chart is available on line).
You will have fun calibrating. There are so many variables involved that it is like a puzzle of some kind. Plus, you get a disc that puts out bass that is ridiculous. I feel terrible for my neighbors every time I put out the meter and role on the disc with my VTF3. It can really put a shakedown on you. If your sub can play below 20hz, the sound waves can even be a little uncomfortable feeling. Its really cool!
Just get em. Its a cheap investment. And you will certainly use it more than once. Experimentation leads to better sound. . . hopefully!
