Rush wasn't even mentioned in the OP, bit of a surprise to me. Rush-inspired, and truly amazing prog rock albums in my book, are early Porcupine Tree offerings Up the Downstair, The Sky Moves Sideways, Signify (listed chronologically, one of them in bold 'cause it's so damn great). I only just got into these recently and it has been a real treat.
I've been an Opeth freak since forever, and love everything they recorded up until Ghost Reveries. Watershed didn't help matters either. Still Life is probably my favourite album all genres.
I've done a fair bit of listening to Dream Theater, but always liked Symphony X better (love those guys!). It is a stretch to call the latter progressive, but to me there are some aspects of their music that warrants it, even though they're definitely more towards the neo-classical.