I recently bought a Fosi Box X5, after yet again needing to fix up a kit tube phono stage, this time for hum.
I noted its easy ability to swap an op amp in it, and wondered if any difference I might hear would be me expecting to hear a difference or not. My new bias is, it's had a couple weeks to settle in, and while it's not as spacious sounding as my tubed options, it's also more even across the board.
I'll just leave it as is. Subjectively, if a swap makes a difference, I think it could make it sound better with my speakers, worse, or no difference I notice.
The point someone raised about it possibly already using fake op amps is interesting, but so far the reviews I've read have all been positive even if it's so.
So I'm going to leave it as is.
As I noticed with my Hypex ncore 122 power amp that uses ne5532 , using it as a plain unity gain buffer makes it rather good sounding. But if one uses 15db or more to amplify the signal using 5532, there is an audible difference between ne5532 and opa1612 . In this case, the ne5532 is not, in my opinion, good enough to use with high performance gear.
I'm guessing all the music in your collection is not good enough for use with high performance gear either. Almost all of it has passed through 100 or more 5532s in the recording chain. It's odd you can hear the impact of one additional 5532.