I'd be careful about pigeon-holing Circus Maximus as a DT clone. Yes, their first album leans very heavily on the I&W-era of Dream Theater, but I think they really took off on their own direction with "Isolate" which sounds very, very different from "The First Chapter" Then on "Nine" (their most recent album) they made another rather drastic change. Honestly, they almost sound like three different bands with the same lead vocalist.
I forgot to mention a band that I think draws significant influence from Dream Theater but doesn't sound exactly like them is a group called Silent Memorial - they have an album called "Retrospective" which is pretty cool. The vocalist is outstanding, he also sings for a band called Cloudscape. I find their catalog to be a bit spotty, but their album "Global Drama" is pretty awesome.