Adam's Ultimate Top 20s: Progressive Metal Albums

Adam's Ultimate Top 20's is a small scale list series where I document with extreme prejudice what my current top 10 of any given subject are. I place the subject matter on extreme scrutiny and all the titles I think that not only the best of the best, but will also stand the test of time, will be listed.In this list I avoided any band that I associate more with black metal, death metal or power metal etc. Extreme prog like Opeth was allowed though.