Hi,
I've only done the Viper once, but the format includes a couple of step segments from C&W and Imax 2 and then a few weight segments from Muscle Endurance, so any type of circuit training would probably work. I bet BM2 would be a good choice because of the power circuits that kind of resemble the interval blasts on Imax 2. I haven't tried that particular BM2 premix yet, so I don't know if core work is included, but there is NO core work in Viper. Hope this helps.
Sara