15th Wedding Anniversary Help

My wife has been eyeing Cartier watches for a while, and I’d love to surprise her with one for our anniversary.

Her biggest hang-up has been cost since she doesn’t really want an all-steel models because she primarily wears gold jewelry. Though her engagement/wedding rings are platinum, but for whatever reason, she’s pretty set on having some gold in the watch. She likes the two-tone look, but the price of a new gold and steel Cartier is more than she’d ever be willing to spend on a watch. I haven’t been able to casually ask whether she’d consider a steel watch on a leather strap, but I’m assuming probably not lol.

So I’m debating between two options: New small two-tone Panthère ($10k) or a  pre-owned two-tone Tank Française ($4-6k)

On one hand, I could save $4-6k going second hand, but on the other is a used watch that special of a gift? And that brings me to another dilemma: if I buy the Panthère new from Cartier and give it to her to open, am I robbing her of the Cartier experience? Or would it be better to set up an appointment at Cartier and surprise her by taking her there to pick it out? My only concern with the latter is that once she realizes how much I’m about to spend, she’ll probably try to talk me out of it. 😂

What would you do? New Panthère vs. pre-owned Tank Française? And would you buy it as a surprise or make the Cartier experience part of the gift? TIA.