Great to hear from you. My experience swapping Discrete OpAmps is that you can vary the overall "sound" but typically not the frequency response. The changes tend (in my experience) to have more to do with distortion and headroom. Typically the transformers are the limiting factor for low end on those preamps.
Here is a Gearslutz post discussing some discrete OpAmps with audio files comparing them.
If you end up trying a different one, I highly recommend creating a repeatable set of recordings that you could do with the OpAmp choices you have. Posting back here would help the rest of PLAP community.
I hope this helps, post again if there are more details I can help with.
- This reply was modified 3 years ago by Michael Stucker.