This topic was discussed in another thread, albeit with a twist, but it is still the same question:
https://forum.audiogon.com/discussions/what-class-a-is-better-sugden-fpa-4-or-pass-labs-xa-25/post?p...
https://forum.audiogon.com/discussions/what-class-a-is-better-sugden-fpa-4-or-pass-labs-xa-25/post?p...