"The problems that I am having with the sub not producing mid-bass, at all, can now be proven not to be a mistake with the wiring as I plugged my old sub up to my iNuke 3000 using the same cable that I have with my Marty Sub, and the older sub sounded great with the same cable."
sounds like you got the cable working. the screw in the neutrik is supposed to contact the wire directly, but maybe there wasn't enough wire in this case.
it is still a mystery: "am having with the sub not producing mid-bass, at all,..."
like worm mentioned...if everything else is good, the amp, the eq, the wire, the driver, and so forth...it comes down to how well you put the box together and mounted the driver.
do you have lots of air leaks around your driver?