Ask away my friend no worries, let me start with the sub, I'm satisfied with it, but it's no powerhouse. It adds nice low end, but its not able to hit super low frequencies. I'm thinking about trying to fit the Rockwell slim 12 box back there instead, there might be just....just enough room.
After months of living with this system I'm still bothered by excessive treble (even after cutting the front tweeters). The only way it sounds good is via Bluetooth where I can use my phone's EQ to cut out the super high frequencies. I have my treble at maximum negative and still I get piercing highs over Android auto or XM if I turn it up super loud. It's either just the way infinities sound, or IMO the stock 6 speaker amp is just blowing up treble internally since it's tuned to compensate for not having any tweeters at all stock.
So over Bluetooth I am satisfied with it, over xm or Android auto it's annoying. It sounds good enough but I know it's not perfect. I'm either going to cut out the tweeters in the rear 3ways, wire in some filters, or break down and amp the whole thing, I just don't really want to throw more money at it since it's pretty much "good enough". I can't tell you about the infinity dash speakers, although seeing as my other infinities gave me treble issues I'd be hard pressed to try them.
I think I was MOST happy before I replaced my rear door speakers.