Check out
www.progarchives.com <---really great selection of mp3s from a huge, and in cases obscure bands.
Blackwater Park is not particualrly good, in my opinion, though not bad either by any means.
About the only prog. band(apart from Camel) from Mikael's reccomendations that I like is Permiata Forenria Marconi; has a very similar song structure as that of Opeth.