A lot of this is my opinion, but here goes...

- First off, I would not want to be locked in to Priority Club for my hotels. I'm not saying there aren't some great PC properties out there, but I would never craft a European vacation around their availability. For hotels, I prefer smaller boutique hotels with a bit of local flavor. That's personal preference: in the U.S., I love the consistency of Marriott; when abroad, I love the exact opposite: something that doesn't feel like a big American business hotel. So I always assume that I will be booking and paying for my hotels, even if my budget sends me to the two-star type properties. (Sometimes I like those more than higher-ranked / better-marketed properties.)

- Second, flights... Since you are looking for J class to Europe, chances are good that you will need to look at multiple airlines - and out of Atlanta you might find DL totally off the board. So instead of doing a DL Amex, why not do SPG Amex instead? That way you not only get a lower annual fee and a better reward rate (1.25 miles per dollar instead of 1, since you are talking large conversions), but you get the flexibility to pick from any one of many airlines. Everybody except UA is on the board for the Big Six, plus you get Alaska and most of the major Europeans. And worst case...you either find nothing or you find DL flights and use existing miles, now you have some hotel stays you can pull from if needed.

I used to carry airline cards, but I decided not to allow myself to be locked in like that. Now the only two CC's in my wallet are SPG Amex and Marriott Visa. (HH Amex and a cash-rebate Mastercard are in a drawer for use when promos call for them.) I doubt I will ever carry an airline card again except when I'm quickly cycling through it for sign-up bonuses.