Modify Threshold SA/2, or buy a Pass Labs X250.5?

Dear Audiogoners,
Currently I have a pair of Threshold SA/2 monoblocks, considering either sending them to Jon Soderberg to modify, or buying a Pass Labs X250.5. Will the sound improve significantly if I replace SA/2 with X250.5? or I should have my SA/2 to modify? I prefer lower noise floor in my system and with more balanced sound. In addition, my source is CDSD with DAC6e combo, will the sound imporve a lot if I connect them with balanced cable instead of interconnect?
please give me some suggection, thank you!
What mods are you doing, if sent to Jon?
My Pass Labs X-350 really prefers balanced lines as the are definetely what Pass also recommends in the manual as well. They were designed that way with single-ended being second. Much higher gain as well is the benefit.
Hi Jpainter236,

That's what Jon suggested for the modification:

Installing Cardas Binding posts, new main caps and IXYS fast recovery diode rectifiers.

Do you have any better suggestion for the modification? also, if I ask him to add the balanced input, will the monoblocks have better sound?