If it is only for classical music, try to look for headphone focus in in treble and bass rather than mid. Focus in mid is good for vocal but may make the instruments sound blur. To me, classical music like orchestra and vocal are 2 different area to cover.
And classical music needs big sound stage to perform well. Headphone like beyerdynamic DT990 perform quite well in classical music but it's definitely not for portable and it needs better amp to drive as well.
Understand that you need it for portable use, but even if you spend all RM1.5k budget on headphone, your hand phone as a dac is a limitation.
This really depends on whether you want to upgrade in the future. If yes, then get a good headphone and upgrade other gears later on.
Else I rather you just grab a ATH M50 + fiio x3 /x5.
Sennheiser momentum and emperor are said to be easier to drive version of HD25-i-ii. With good amp, hd25 is definitely a better choice. (Or beyerdynamic DT1350, more refined kindly of sound.)
Sennheiser momentum to me is not a very balance sound headphone. Quite focus in mid, mid is slightly forward, bass is not very punchy, treble expansion is not so much. Suitable for pop and vocal but not big production.
Sennheiser Amperior is more suitable for classical, powerful with good dynamic. Mid bass is quite rich. Probably can go for this. I'm not sure how good E12 can drive it. I just tried it on other set up.
The rest of the headphone listed, KEF is a quite decent headphone but don't think you should go for it as you need headphone that has lesser needs in amp.
Bought the amperior, had been using it for an hour, the sound is thin out of the box, maybe needs burn in? The sound is balanced and detailed though