I have mm6501's in front and mm651's in the rear, running 2 mm840 subs. I initially had the subs wired for 4ohm and then decided to rewire to 1ohm. The issue I've been having is the amp seems to pop protection at lower volumes than I found to be the max these subs can handle. It's intermittent, one day they can reach louder volumes fine. I also been noticing that sometimes the whole system will sound muddy and I'll notice distortion at even lower volume. I'm not sure if I'm looking at a faulty amp or not. I've been also thinking that I need check and see how much voltage the amp is getting when this is happening.
My wiring is pretty good, the ground and power are both 4 gauge and the ground measured low resistance.
Any other things that are worth checking out?