I'd suggest Shure Shr840 / shr 440 or AT M50, these are more all around types of cans and sound fairly good even unamped.  

If you convert 128 kbps AAC to Flac you will get the same ACC quality in a much larger file. But if your dap isn't able to read ACC this is the best option to keep the original (low) quality. If you convert ACC to MP3 or OGG you will have a sensible degradation of sound quality due to...

Yes, 320kbps mp3 files do really sound better to my ears. May be that if you could listen the tracks using wasapi you'd be able to hear a larger difference.

HD 280 offer the best isolation, then in order: HD25 II, HFI 700, M50, Pro750/900, K271, D5000/7000, DT770 (600 ohm). I have not considered in the list any open or semi-open cans. Unfortunately HD 280 are rather unconfortable because of their strong clamping force and I don't like their sound...

 

Using 7000 with  Lehmann Black Cube and very happy.

  Symphony No.9 in D minor, Op.125 Gabriela Benackova (soprano), Marjana Lipovsek (contralto), Gösta Winbergh (tenor), Hermann Prey (bariton), Konzertvereinigung Wiener Staatsopernchor, Wiener Philharmoniker, Claudio Abbado DG 419 598-2

Mario Biondi - If  

     

Beethoven S.9 -  Abbado, Wiener Phil.  

I prefer earbuds over iems unless isolation is a must (and there are a lot of better isolating iems compared to IE8) so if I 'd have to choose one, my choice is MX980. These are amazing sounding earbuds.

I listened  HD25 SP in a shop time ago and I did not like them very much. Recently I bought HD25 II for portable use and though I have better sounding cans for my home rig  I'm quite satisfied with HD25 connected to Cowon D2 or J3. Cannot compare the two models but think the  higher price is...