In addition to what everyone else has said, focus on being a TEAM with your wife.
You don't think money is an issue when it comes to you getting a new car. If your wife agreed, then money would be off the table. But your wife doesn't agree. Since your wife and marriage are more important than a car (at least they should be) then the price of the vehicle is back on the table.
If it matters to HER, then it matters to the marriage and thus, it should matter to YOU. If money is a concern for her, then it should be a concern for you. Her feelings are equally as valid as yours. They are just as much her finances as they are yours, and though your threshold of an acceptable expenditure is higher, it would be cruel to hold your wife to your threshold.
You have predetermined what kind of car you want, and now you identify yourself with that car. Your wife's rejection of the car is seen as a rejection of you and your worth. This is the problem with coming up with a solution on your own. You become invested in it and see it as a part of you. How can your wife argue with that?
Same with the job. You've decided that this job is how you will be most fulfilled, when this job isn't about you. It will affect your wife as much as it will affect you. By predetermining what the ideal solution is FOR YOU, you have made it so that any objection your wife has of the job is an objection and rejection of you. So she isn't safe in expressing her hesitations.
Any problem she has with the job, the car, or whatever issue you POJA is now no longer a matter of her feelings and comfort and desires, but rather it is cast in the light of accepting or rejecting her husband.
Talk about lose/lose.
So think about what it is you want.
Is it the features of the car? A certain aesthetic? Being able to feel rewarded for your hard work? What does the car represent? What values does it represent? What is its meaning to you?
What it is about the job that would be fulfilling? Is it the work involved? Is it the sense of accomplishment? Is it the admiration and respect it will garner? Is it the challenge? What values of yours does it express?
These are the things you should talk about. Not about why her objections or reservations are unreasonable or silly or unimportant.
But what do these things mean to you? How can you find other ways to achieve the same goals, express the same value, meet the same needs?
Maybe this job meets a need for admiration, but maybe your wife can meet that need instead. Maybe the job gives you a sense of fulfillment, but that fulfillment could also be achieved through volunteering with your family. Maybe the car reflects a certain status that you have achieved in life - maybe you can achieve that by spending less money or by saving up a certain amount for x months before purchasing, or opting for a longer repayment plan that fits into your budget.
When you distill what these solutions mean to you and what they reflect about your wants and desires, you can get to Guideline 2 and REALLY identify the problem, and only THEN can you reach a satisfactory agreement.
If you don't know WHAT it is you're fighting over you will never find the solution. Often, what we THINK is the problem, what we THINK is the issue is only masking what the true problem is.
This is why predetermining the solution doesn't work. It is why it hinders REAL negotiation and problem solving. Because then you argue why your solution is better than your spouses without ever really defining what the problem is. It is why you will both be left feeling unsatisfied.
The car you buy, the job you work, BOTH will affect your wife. They both will have an impact on her life. She gets a right to say if she is comfortable with that or not, and if you put your desires before her she will always know that she is less important than your car and your job. Your wife has just as much a right to determine the events of her life as you do.
Seeing her as a roadblock to achieving what YOU wants makes her your enemy.
Do you really want that?
Do you want the woman you love, the person you should care about more than anyone else in the world and who should love you the same, do you want that woman to be your enemy?
Because that's what Independent Behavior does. It creates enmity between you and the person you should cling to above all others. It puts her in the way of having the perfect life you crave, when really your life would be imperfect without her.