no complaints at all on my end. Well they are way more smooth than I was used to then my HDCs. A lot lower distortion in the sound so it might not be perceived as painful but its definitely a lot louder and waaay cleaner sounding. Not really a con, just something you might need to get used to SQ wise. Havent gotten the coils anywhere close to warm yet untill i do a lithium swap and go hard on them.
You can run either of those subs, they are all built by FI literally the same class of subs you wont notice much difference at all. You'll get them made and shipped out a lot faster than SSA though lol. My buddy is waiting on his order for 3 months and still no evil 15s which are basically the same as the crossfire xv4s as stated by dan from FI just different bottom plates.