A few comments prompted by posts in this thread:

Don't overemphasize the cost of an annual fee. This is especially true for hotel cards. You can easily recoup the fee with the yearly bonus. For example, Priority Club Visa has a $49 annual fee but gives you a free night certificate at any IHG hotel. Easily worth it. (Similar with Marriott)

In your particular case, the United Explorer card might be worth it, especially if you can't make it to Premier. The first checked bag free, priority boarding, and two lounge passes might be worth the $95 annual fee.

Also, while cancelling cards might have a negative impact, you're probably overestimating it. By a lot. There are many, many people here who "churn" through lots of cards and it doesn't have much impact. If you are not applying for a mortgage where the interest rate of the loan is important, then the negative impact probably doesn't even matter.

For someone like you, who doesn't travel much but wants to sit in the front, there really isn't much of an option but churning credit card bonuses. It'll take years to earn enough from the spend alone.

Let's take a hypothetical example. Let's say you spend $2000/month. You want American Airlines miles. If you use an AA card, you'll earn 2000x12=24000 miles per year. That's just short of 1/2 of a ticket in Business Class to Europe.

Instead, if you used $5500 of that spend to fulfill the signup requirements for the two AA cards, then put the remaining $18500 on a 2% cash back card, you'd have 155500 AA miles PLUS $370 in cash. That's THREE Business Class tickets to Europe plus $370 in your pocket when you get there.

You can easily do even better than that. In my book, that's worth a potential small ding to my credit score from cancelling in a year or two.