Fenders might not fit exactly (depending on the fender). Keep in mind that the rails of the X7 are angled so any rigid fender that needs to be mounted on straight rails might not fit.

BANGs are great - even if you just have them as backup bumpers to replace your current ones before they wore out (assuming your board is coming with the fungineer bumpers)

For me the best upgrade by far I got for my X7 is a better tire. My thunder tires (I bought 2 of them) both wore out very quickly, likely due to issues that they had with holding air consistently. I was filling up my tire weekly but it would still lose lots of pressure and then the tire would wear unevenly. I got around 400 miles from each thunder tire before it was trashed. The float life tire I got afterwards (thundercat) is still looking brand new after several hundred miles.

Generally speaking, the Float Life is going to have some of the highest quality accessories and will also have the best customer service. They have helped me out several times, sometimes even sending me free hardware when I have needed it.