I do listen to a lot of pops/rocks as you say

and just to confirm, it's same here. I just mentioned this in a conversation the other day; I have some 320's that sound better than FLAC's and it's pop music. I would just add one thing; it is the quality of the mastering, for sure, but I suspect it is the ripping process as well.
I am yet to confirm this ripping business, I'm not there yet. What leads me in this direction is one case where two identical ripps were made from the same mastering/source. One was awful. I have no means to exclude the possibility that one of the rippers was laying, though.
editinig just for the sake of the conclusion; I think 320 is 'big enough' if you do everything properly. Since you can not rely on everyone putting in the effort, I dl FLAC's simply because I see fewer bad apples. If it is lossless or exact copy, it should be all there.