Hey welcome aboard Scar! I haven't been on here in awhile, but I'm sure you'll love the forum. There's lots of great people and very interesting conversations.
You've got a lot of good suggestions and a gold mine of music to listen to. I agree with Roedent; "dive in!" It's all good!
My 2 cents though.. Dream Theater really introduced me to Haken, Yes, Rush etc.. I'm thinking if you like those bands, and with the songs you listed that have struck a chord, then I would suggest: A Dramatic Turn of Events, Falling Into Infinity and Octavarium.
Of course going with The Astonishing you'll have a better understanding of a lot of the current threads and have more to share. My suggestion for this album is play it all the way through in one sitting like you're watching a movie. ... Better yet go see it in concert if you can. If that would be your first listen that would be epic!
Once again, welcome!