Aside from I&W, I also really like Awake although that one is more metal and less prog. After that, I guess the next three albums were alright, but then they just became boring, their sound has became so stale... but I digress, what I wanted was to make some suggestions for when you choose to re-listen their stuff:
*I&W is DT at their peak. Nothing more, nothing less.
*Awake puts the metal in "Prog Metal", less original but most tracks don't bore me despite their length, really curious about what you'd think about this one. Scarred for example is pretty haunting to me.
*Falling Into Infinity is a more diverse album, but probably derivative from your POV. Still, I wonder what you think about "Trial of Tears".
*Metropolis Pt. 2 has some great moments but it's also very very self-indulgent (this seems to be the Rudess era trademark). I would definitely recommend not listening to this one before I&W and Awake, heck even FII would be better.
*Six Degrees of Inner Turbulence, more like Six Degrees of Self-Indulgence... to be frank, I could live without the first CD (yes, a DT double album) but the second CD has the SDOIT suite which I actually enjoy and am curious as to how you'll feel about this one. Definitely the last hurrah before the band went on to try and make each album more complicated than the last one while disregarding the songwriting.
Woo that was a long post. Well, let me know what you think about Prog Metal's (supposed) premier band. Later.