I know this is only a forum but this entire thing seems a bit shady to me. Why hide it from your wife? Does she hide things from you? I would personally recommend having a discussion with your wife, explaining why you need it and listening to her reasoning about why this is not a good purchase for you? At least then everything is on the table. Maybe you really don't need it, or maybe you should agree to sell something else to help you raise the money to purchase it.
Don't get me wrong, my wife and I don't always agree on these things either. I bought an M6 a while back that she was not in favor of, and still isn't. I already owned several nice rangefinders and she could not understand why I needed this one. Actually she was right. I really don't need it, but I do enjoy working with it. However, it was not a surprise when it arrived. I agreed to sell a couple other things to help defray the cost and, though she still is a little irked over it, she accepts that I wanted it and didn't blow the rent money buying it.
Obviously this is only my own opinion and everyone else is perfectly welcome to completely ignore it if you want. The fact that my wife and I have been happily married for 39 years should in no way effect your decision.