My first exposure to Dream Theater was when a friend of mine played Images and Words for me at his house; this would've been Summer 1995. I was blown away, and asked him if they had any other albums, and he said they only had one, Awake, which he also played. (He wasn't aware of WDADU; as far as he knew, those were the only two albums.) I'm a prog guy at heart, with some leanings toward heavier rock, but not really metal. But this was fucking amazing music, something like Yes meets Metallica. Complex compositions with keyboards and unusual time signatures, but also crunchy guitars and wailing vocals. There's a reason Dream Theater is often credited as basically inventing prog metal.
Their new "album" had just come out, A Change of Seasons, which I didn't realize was an EP with the title epic and a bunch of covers, but I didn't care. I bought it from the local Best Buy, so it was my first DT CD. I'd ordered IAW and Awake the from record club because obviously I had to have my own copies, but they hadn't come yet.
I put Awake as the era because it was the closest album in the list. But that's only because ACoS wasn't listed, and I think of the early stuff (anything pre-Jordan) as the IaW era.