I've only been married a few months, but in that time I've put more effort into my training, cardio and diet than ever before....
.... I don't ever want to be the fat, slob husband who sits there munching chips while watching Sunday football. The type that the wife looks over at and thinks "I could've married James Harrison.... and he's a DENTIST now."
That scares me.... I always wanted to be the best I could possibly be for my wife, but more importantly.... myself.
I think you should do what is better for you. I don't know anyone who doesn't feel better about themselves when they're lean, as opposed to when they're carrying fat. It boosts your self-esteem and makes you feel good.... and when you're cut, if you ask yourself if it's worth the cardio and the dieting, you'll probably agree that it is. Ask yourself when you're still carrying some fat, and the prospect of cardio/diet doesn't look to appealing, regardless of the rewards.
In terms of marriage, think of it this way: What would you think if your wife completely let herself go, stopped exercising and watching what she eats, stopped wearing nice clothes or make-up.... with the mentality "I've already bagged a man. What's the point?"