wow..... that's alot of problems......... have you taken a reading on the mid you believe is blown and seen whether it shows open or a high resistance, or hook it up to a different source to be sure it's blown? just curious... anyway, that's one long list of troubleshooting..... VERY good for you, glad to see you're putting forth effort to resolve the problem, so many people just blame it on bad equipment and go change everything out......... which brings me to the point of wondering: 1. When you checked the RCA's did you try a different set to see if it got better? 2. Did you check the wiring going to the speaker from the crossover for shorts like the other guy asked? 3. Have you tried a different HU or amp to see how everything acts with the equipment changed out? 4. Have you tried hooking up a speaker temporarily to the different channels on the amp to see what it sounds like with the wiring out of the equation?
I ask all these questions because I believe they should be the next steps in troubleshooting the problem(s) if you've not already done them..... I say problem(s) because in all actuality it sounds like more than one to me and usually the easiest way to find out what's wrong is to start at the beginning and check each link in the chain one at a time.....