There are many opinions as to what defines "progressive rock." A check on the link "Progressive Rock Archives" will give you an idea of what I mean. For me, it's music that is just really great. It's rock music by people who seriously enjoy playing their instruments--not people who are just interested in partying or making money!
Among my favorites in the genre are Rush and Dream Theater. After watching and listening to the DVD "Score," Dream Theater's final concert on their 20th anniversary tour in 2005, I decided to get a copy. It features the Octavarium orchestra, including a brief flute solo by a woman who received an ovation from the fans at Radio City Music Hall. (There's something about progressive rock fans--at least, Dream Theater fans--they have class!)
I think if Jesus were walking around today looking for a band to play in, and I admit some bias here, he would be totally prog!