The RPM looks to be a good unit with good sample rate and expandability. The Innovate stuff is the best bang for buck but what lets it down is the sample rate if you want to use it for suspension work you'll need a much higher sample rate than 12 samples per second. The RPM is 100 samples per second and that's a big difference.
Check out Motorsport Innovations he's very reasonable and offers great pricing. MSI Home
I got my innovate set up from him when he was still selling that stuff.