Edited by combataran - 12/28/12 at 8:30pm
I can warmly recommend AKG K601 and Audio Technica ATH-M50 for classical in your price range. Personally from what I have heard from Grados I think that they usually have kind of odd balance for classical music. I have not heard the models that you mention but I have heard some pricier models.
There is one thing you need to have in mind, no matter which of these headphones you choose. You will need an amplifier to drive them.
I have several of the Prestige line of Grado. Honestly to me, they are more similar than dissimilar and really only generally recommend you get whichever is the least expensive for you. I don't find the higher number to equate better sound, more like different flavor. For example the 325i doesn't mean it's better, it's just another sound honestly, but a very similar one even. Lots of people have a preference for one or another in the line. I generally again recommend the least expensive and recommend the L-cush pads be a mandatory purchase for the 60i/80i.
Now, as for using Grado for classical, that's entirely preference. Me, I would not. Why? Because frankly they're just uncomfortable. They sit on-ear, not around-ear, and they have rather uncomfortable pads and pressure points (especially if you wear glasses). The sound is excellent. But they also do not have the best imaging out there, and imaging/soundstage is critical in my opinion for classical music (this is in reference to you being able to pick out instruments and their perceived location in an ensemble and distance between you and the instruments). Grado is a very in-your-face sound stage and a grainy sound in general. I love it for violin and cello, it has a visceral meaty sound for it. But for a Sonta or something, I would look for another headphone.
Depending on your budget, I would suggest you look at a headphone like the Beyer DT880 or Hifiman HE-300 r2. Not sure about prices in your country, so might have to dig around. Otherwise, maybe list what's available where you live and in your price range so we can help recommend something else.
Oh, and the M50 is the anti-thesis to classical music. Avoid.