From my experiences, I think the combo you've got with the HD-580 and MG Head (with upgraded tubes) is a great combination... There's just some awesome tonal, warm quality to it. Although the resolution could be clear and faster, but that would require you to upgrade to a much better tube amp.
Like the suggestion above, the Gilmore is a very refined, but definitely "solid state" sound, it doesn't have the same tonal warmth as the MG Head with upgraded tubes. If you like the sound signature you've got now, especially the warmth, you might find the Gilmore disappointing. However, Gilmore is very versatile, and very "punchy"... If you've got some headphone more geared towards rock/upbeat stuffs (CD3000, Shure E5c, Grado SR225), the Gilmore is a great fit with those headphones.
Now, with all that said, I'm not sure what you would "gain" if you were to move to an Ety. You would definitely get better isolation for the college environment, studying in cafe, library and what nots... but otherwise, I'm not so sure Ety ER-4P/S would give you a much better sound than what you've already got now.
Some people can have a preference for the Ety sound, but personally I don't think the presentation and the response of the ER-4P/S varies that much from the HD-580... and the comfort factor definitely weighs in heavy favor of the HD-580.
If you were lookin' for roughly the same type of sound in a different form factor, then I think the Ety ER-4P/S is a good fit. If you were looking for more excitement, something "different".. I think you should look into some other options.
Perhaps trying out a Grado, or an Audio Technica... I've tried the Grado SR225 before, and found them extremely response and exciting. However, the comfort factor made me decide to pretty much, never, get one (and they're a bit too intense for a long session). I've got a Audio Technica A900 on the way.. should be here in another week or two...