I bought a new chain and sprockets not long ago and stayed with the 530 and 16-43. I have been thinking about trying the 15 and not sure if I want to up the rear 1 or 2 teeth If do it. I have been happy with the stock gears so far (I do not mind buzzy)
I cleaned and lubed it regularly (every week) and in general ran it on the loose side of the adjustment. I finally got the the end of the adjusters and it still had way more sag than I'm comfortable with. I thought the 520 conversion would be a fun change of pace.