Noticeable difference when switching from 525 to 520 chain setup?

For street.. no, for track yes.

For street use I'd stick with steel. The chain won't make any noticeable difference on the street either. If you can get a deal on a set and it needs to be changed then I'd switch to 520 but I'd stay with steel if you are not going to use it on the track.

I use steel both on the street and on the track (520).