That is basically the same decision I've made, although I haven't gotten the Explorer card yet. I'm absolutely holding on to the MP Select Card, and I closed the MC.

While not UA specific, I also heavily utilize the Chase Sapphire Preferred card to transfer ultimate rewards to United and have no foreign transaction fees. The Club cards don't have much value to me because virtually all my travel is International, and thus I can get into the lounges for free.