If for classical, the 880 is nice but to me my closed dt660 beats it. Maybe my ears are screwed up, but i EQ dt660 down few db (40hz and below), and then its a super clean super flat response. I dont get why it beats my 880 (250 ohm edition). Possibly my amp /dac. IIRC David Mahler said the K701 is even better for Classical ( I will see if i can find quote) . K701/DT660 combo doesn't sound bad to me. I have not had K701, but would like to down the road. Its possible dt880 600ohm is even better than dt660 for Classical with right amp/dac. There is risk and heartache in this journey trying to find right sound. But dt660 won't break bank (79$ US). I still cant believe how neutral it is

, makes dt880 seem bassy, and we know they are not that bassy
I also recall someone saying dt860 midrange was near/superior to dt880. But I have not gotten a pair . Same driver as dt660 but open design. Rarer now to get. And even dt440 some prefered to dt660, but i have both and disagree (for classical music types anyway) dt660 is the flattest, neutral one i have (with EQ, its magic) . As below 40hz its useless, so better to reduce even more (less chance of it interfering at higher volume.)
"I think as I've lived with them, I've come to realize that the DT660 excels over the K701 and K501 in the sense that it is closed back with superior isolation. In an ideal setup with a really good source and a powerful amp, I would still take the AKG except in certain orchestral passages." - David Mahler
Post # 79 of 405 in Thread: i-truly-believe-these-are-one-of-the-best-classical-music-headphones-ive-ever-heard
Also the dt660/860 are 32 ohm, and work great off a portable/ laptop. It defies all logic. 880.600 and k701 prob need some beefy sources/dac/amp etc. Good Luck