I don't know, its hard to say. But to get an Idea of what they were into when they started out, I have taken this quote from their Biography..
John Petrucci (Guitarist) influences :
"The encore was indeed a work of genius; a medley of the instrumental breaks from classic songs from the likes of Led Zeppelin, Yes, Queen, The Beatles and Van Halen."
Steve Vai, Al DiMeola, Alex Lifeson, Steve Howe, Alan Holdsworth and the late Stevie Ray Vaughan.
John Myung (Bassist) influences :
Chris Squire, Steve Harris and Geddy Lee and their respective bands Yes, Iron Maiden and Rush. He also listens to bands like Jane's Addiction, King's X and The Red Hot Chili Peppers as well as classical and blues.
Mike Portnoy (Drums) influences :
Rush drummer Neil Peart and the late Frank Zappa. Other favorites include drummers Terry Bozzio, Vinnie Colaiuta, Simon Philips, John Bonham and Keith Moon and bands such as The Beatles, Queen, Yes, Metallica, Jellyfish, Iron Maiden, U2 and Jane's Addiction.
Jordan Rudes (Keyboards) :
His biograpgy isn't as clear cut as the others (thats where I've been getting this stuff from :p), so I'll describe him, he grew up on Bach, Chopin, Beethoven, and has now seemlessly blended his classical style into progressive rock) AWESOME!
James LaBrie (Vocals) :
James' musical tastes are quite varied as he names Metallica, Aerosmith, Van Halen, Journey and Judas Priest as well as classical composers Mozart, Vivaldi and Beethoven as favorites. Influential vocalists include Steve Perry (formerly of Journey), Freddie Mercury, Sting, Paul Rodgers and Nat King Cole. James continues to practice with Ms. Burns and encourages other vocalists to pursue formal training.
Well there you have it, should give you an idea of the band and their quality [wink2]. After my effort, I hope your gonna buy their CD's :D