Get what you want and say, "Get over it." She will.
I would have serious questions about a relationship in which one of the parties could not understand or would not accede to something as important as music. This isn't a matter of tolerating the disease of audiophilia. It is about honoring and respecting things that are important in each other's lives. Any time I hear someone say (speaking of SAF), "I can't have" or "she won't let me have" I start to worry. Healthy relationships are grounded in "I would prefer" or "have you thought about?", not in "you can't have!"
In the days before your prelate discovered the ineffable joys of celibacy, he was married to a remarkable woman of many virtues. She had, alas, a tendency to say, "You can't have." Unfortuantely for her, I was just as adamant and built my sound system, anyway. I made sure I was as responsive to her interests (horses) as she was to mine. We had some rounders for sure as both of us struggled for dominance and control but in the end I learned to love horses and she learned to love good audio.
IF you are behaving reasonably in the matter of money, etc. then stand your ground and tell her, gently and supportively, that she'll just have to adjust. And then give back to her the same kind of support for the things important in her life.
Will