Might as well post up some shots of some balanced Grados (old SR80's). They've been recabled to 3.5mm to 3.5mm female dual entry detachable cables that terminate with 4 pin XLR. I'm using a 500ohm resistor with the Emotiva.
I expected the treble to be hot, but it actually isn't on my setup. But I have considerable warmth on my overall setup. Perhaps the resistor helps a touch too no that front. Good energy, not dark of course, but it doesn't cut you in half in traditional Grado style. Then again this is an older SR80, not one of the new ones. The mids are excellent, very realistic, very Grado. Tons of energy, great forward nature. The detail is quite nice, tons of separation, not congested, a touch of the Grado grain sound is there, the house sound at least I find with most prestige series, but it's quite clear otherwise. Instruments, melodies and vocal sound great. There is a little edge to the upper mids with vocals, even at normal listening level, the forward nature of the Grado mids comes right through, be it a guitar solo, or a vocalist belting a solo. The energy and emotion is there. Nothing close to flat and boring or dry. Tons and tons of energy, but controlled. Fantastic. The bass is typical for Grado. I'm using L-cush pads, as I prefer them and find they are best for total tone and are the best when it comes to lower frequencies. Without any equalization, the bass is there, nice, tight and strong. It's not a subwoofer naturally, but it drops fairly low for an open air headphone and a Grado in general. Great punch to it. I would not describe it as polite at all. It's not out right bassy, but it's there where it's supposed to be. I'm pretty much a bass-head and this is satisfying enough for the kind of music I like Grados with.
So you can definitely use Grados with a speaker amp like the Emotiva with an adapter like the one I described and use. The 500ohms matches great with the Grado. No noise floor at all, no hiss, and it doesn't sound tame either. It actually sounds a lot like a loud speaker does, with focus on mids and just raw energy. Grados really portray what current from an amplifier is all about.
When I equalize using my typical setup, I drop most frequencies, flat across the spectrum by a good -10db and leave sub-bass at zero and curve down from there to mid-bass. I drop mid bass too, I only equalize to bring out sub-bass, because I find that is where most open headphones lose their thunder. And I happen to enjoy sub-bass the most. As a basshead I actually dislike strong mid-bass, it's annoying and boomy. But sub-bass that is as volumous as the mids is amazing. So I equalize for flat to slightly emphasized sub-bass, at least, to my ears. Someone else might think it's "bassy." I like it like this because bass guitar and kick drums just really pop with the sub-bass running hot.