I wasn't too crazy about Gloryhammer (although I'm sure I will enjoy them live) but Stream of Passion is a solid A+ from me.
Curious about why you announced the #2 band, and not the #1 band first?
Since people are posting about who they'd love to see on the fest, i'll second Threshold, but I'd also like to throw Pharaoh into the mix - one of the greatest American metal bands of the century IMO. I'd also love to see some of the bands of 2015 that had to drop (particularly Anubis Gate, Morgana Lefay, and While Heaven Wept) get another shot at playing ProgPower at some point.
Also, PROGTHRASH - Heathen, Mekong Delta, Toxik, Blind Illusion, Voivod, Vektor, Sadus, Helstar, etc. - as for power metal, I'd love to one day see an After Forever or Power Quest reunion, if either ever happen. And of course, Fairyland + Dark Moor. OKAY, enough fanwanking.
PS Milton, it was cool actually getting to chat at Riverside in NYC. Was a great time, and I am so thrilled I got to see one of my favorite bands twice in a week. Cheers.