My wife knows next to nothing about music gear and the topic bores her to death. Therefore, our solution is to have different budget categories for each of us that roll over each month. She has subcategories for things like beauty (nails, hair, cosmetics, etc.) and I have subcategories for clothes, lunches out, and music gear. This way, I can decide what music gear to buy and as long as there is enough money in that subcategory, I don't need to discuss it with my wife beforehand. This method has been a real marriage-enhancer.