I am in the same boat. Primes will be the last headphone I purchase for awhile. What amp are you looking to get? I like your description of the 480. I will check them out. I am unfamiliar.
Yeah, probably a Lake People/Violectric amp, haven't decided on the model. Not much info is on the DT 480, I'm one of the handful of owners of one here on Head-fi, I modded and pad-rolled mine for comfort and to tune the sound more to my preference, largely to get more bass presence out of them. Some may not agree with me on them, they are a love/hate headphone, they are all about the midrange and they have a very raw sound and not a headphone you can really relax with like with the Amiron, they demand your attention when listening, even moreso than the DT 1990.
For me the DT 480 are the my involved listen for when I really want to critically listen and get absorbed in the music. The DT 1990 is the middle-ground and my electronic, edm, etc. masters, I absolutely adore the DT 1990's with anything energetic with a thumping bass-line but also really like them with everything else and I do like their vocals slightly more than the Amiron, the DT 1990 are a jack-of-all trades and that euphony/musicality they have. The Amirons are my relaxing, video gaming, movie, tv show etc. headphones and actually get the most use. I use all three headphones a lot actually. Amiron's get the most use just because they are so relaxing and easy to listen to and best when I don't want to get absorbed in the music.The DT 1990 gets the second most use and what I usually use when I'm in a pure music listening mood. The DT 480 gets a little less(but not much less) use than the DT 1990 due to their sealed design(they don't breathe at all with the pads I use), but I use them for when I really want to get transported to another world music-wise.
The reason the Amiron's get the most use is because they wont suck me into a vortex of endless hours of music listening like the DT 1990 and DT 480 can without realizing it making me lose track of time. I'm not saying the Amirons are boring or anything, they are anything but. But they let me actually focus on other things while listening, like I can read, etc. with them playing music no issues. The DT 1990 and especially DT 480 are like "You're going to have to listen to music if you have me on."