So anybody who knows me knows that these guys are pretty much my favorite band. Anybody who doesn't, well... you know now!
I think they'll have a lot of appeal to most DT fans. They can be heavy and proggy and are filled with all kinds of musical deliciousness for you to sink your ears into. Fun fact: Their first full-length album ("Act II: The Meaning Of, & All Things Regarding, Ms. Leading") made Mike Portnoy's list of top 10 albums of 2007.
Their latest release ("The Color Spectrum") is a 9-EP set based on the 7 colors of the rainbow plus Black and White. Seriously... how much more prog can you get?!
Here's something to start you off if you're new: