I agree with those saying to be up front about it, then what can she say.
You'll find out, that's for sure. My wife knew I smoked and drank when we got married, I don't anymore. They don't love you for who you are, they love what they have the potential to make you, in their mind. You don't know what she has in mind. If you did, you may not marry her.
I was curious whether the ladies in their lives were on-board with these purchases or how they managed to convince them that it is normal to drop $15,000 on a pre-amp when most women (generalization) think that Bose sounds fine.
Don't ask, don't tell. I don't consult, inquire, or convince, I just buy it. If she complains like wholly hell, maybe I'll sell it. She mostly complains about aesthetics. She doesn't complain much anymore, since she now knows that her complaints may make the offending piece leave, but the replacement will be more expensive and just as ugly. Do that enough times and they'll stop complaining.
Also, I can't stress this enough, keep a seperate, private bank account and credit card. That way she'll never know how much $$$ is involved. "Oh, it's just a $50 power cord hon".......yeah, right...LOL.
Good luck,
John