I saw AK with US a few years ago. Top notch band with Jerry Douglas? What could be better? I recommend "Best Kept Secret" by Douglas with lots of guest talent. Follow to The Tedeschi Trucks Band. This is getting away from bluegrass, but great music.
Getting back to bluegrass, I really like Del McCoury's new release.
A really interesting mix of bluegrass and other styles are a couple favorites by The Duhks, the self titled, and "Migrations". Both cds offer nice production/sound.