Your wife is not your enemy. She just had your child. Her emotional state may not have returned to normal yet from the hormone shift caused by the birth. She might be more irritable and moody than usual. She also may be having trouble with why you are thinking about buying a Viper so soon after your new child was born. In other words, she may be saying to herself: " Why isn't he thinking about his new child and me?!" She may be afraid that you are headed for midlife crisis land and/or of the Viper and masking that fear behind the four passenger idea. Just properly assert yourself. Explain to her that you understand her feelings on the subject but it is important that she understand and respect your feelings on the subject. Tell her that your desire to have the Viper is not a threat to her and your new born child. Finally, explain that you respect her views but it is important to the emotional health of the marriage for you to acquire the Viper. Then acquire the Viper. All of the foregoing is conditioned on the fact that I am assuming that even with the expenses of a new child that it makes economic sense for you to acquire the Viper at this time. The timing does seem a bit curious. Frequently a husband will start to feel a little hemmed in after the birth of a child and sometimes, especially when they do not realize why they are feeling that way, they act out in self destructive ways. I am not suggesting that you are doing this but the new child/ "I want to buy a Viper now" timing is rather obvious. Good luck whatever you decide to do.
Best,
Bob
Best,
Bob