I'll second The Flower Kings, Transatlantic and Circus Maximus, their last album Nine has some uplifting lyrics. Can't think of any more prog bands with positive vibes because most of my favourite music are very emotional, melancholic and sad if you will, that's just what i prefer. So i'll just add some uplifting songs that gets me pumpin' and in good spirit for the heck of it:
Pagan's Mind - Eyes Of Fire
Allen/Lande - Wish for a Miracle and Come Alive
Nocturnal Rites - The Iron Force
Stratovarius - Eagleheart
Hammerfall - Dreamland
Masterplan - Wounds
Sonata Arctica - The Cage
-and-
Dragonforce - Fallen World (Come on, you know your
smilin' for whatever reason)
So a side note is: you can basically put on any Power Metal album, and your fine.