I've played piano for 15 years (now ARCT performers level if you are familiar with the Royal Conserveratory of Music), and I've played in may ensembles in the past, so like you, I have a trained, musical ear and I know how instruments should sound.
I only own the $97 Grado SR80s, but I've spent quite a while with the higher end $190 SR-225s, and I am particularly moved by violin passages on all grado headphones, because the timbre of the instruments is very noticable due to an extremely creamy smooth midrange and sweet treble. Every texture from the squeak of rosin of a violin's bow to the ring of a piano string in a fortissimo note is audible with extreme clarity and transperancy. Vocals are especially impressive. Though some might argue that grados are not the most accurate phones in existence (there is a treble peak that can be painful for some recordings that I will talk about later), I can conclude that they are the most musical form of sound reproduction I have ever heard.
Most people recommend grados as a rock phone. I personally disagree. Though impactful, the bass doesn't extend deep enough to provide a powerful beat with any authority. Additionally, the lower bass frequencies are looser than comparably priced headphones (DT880s, Senn HD650). Snares and cymbals, however, are well presented due again to the nice treble and awesome midrange.
If soundstage is important to you, I would avoid the Grados that I've tried (I doubt the rest are any different), because with Grados, it is something that is pretty much nonexistant. It sounds like all instruments/vocals are about 4ft away from you. Although things sound incredibly real, the locations of the sources of sound make no logical sense (For example, the drum set in a Wynton Marsalis CD occupies the whole stage from left to right).
Be wary before jumping on the Grado boat. The grados are extremely bright phones, and you might not like them (I didn't like them immediately when I purchased my 80s). Because of an intense treble peak in the 7-11khz range, bright pop and rock recordings are fatiguing to listen to due to EXTREME sibilant accentuation. However, judging from your post, I get the impression that you are listening to a lot of refined ensemble music, for which sibilance is hardly a problem. I would try them out at a local Hi-fi store before purchasing.
All my opera, baroque, classical, romantic tracks sound incredible with these phones. Rock can sometimes be painful, but it's mostly poorly recorded pop with too much reverb (which accentuates "S" and "sh" sounds made in the 7-11khz range) that hurts my ears to the point that I have to discontinue use with these SR-80s.