I switched last year from factory to 60x. I like the strings but did have a 3-5fps loss when I went to the 60x. I plan to try a new company this year, not exactly sure who though.
My 3 season old original Prime Rival string set has been good. I have a free replacement set sitting in WA state 6 hrs from home I will have them put on in a week. Been hunting so no time to change them out.
I bought a second backup Rival that came with aftermarket strings. I pulled them off as the bow was out of spec and the nock fit poor so put the original strings back on it as well. Was not impressed at all with those aftermarket strings, which are considered high quality on archery talk. YMMV. Good luck!