Forgive the ignorance of not having read the entire thread.
But a lot of this looks like "Men helping men", many stories with mixed success.
My guy is practically prohibited from entering any gadget store unsupervised, as he is a salesman's dream. "Really? It has lazer beams...you're right, that would be handy." and we have separate accounts, but are saving for a trip.
A chick tip?
Show her you" thought of the relationship first" (translation, buy her something just as frivolous, jewellery works like a dandy)
And she won't even think about the tank.