I was thinking I could opt for simpler life, sell my other headphones and get the TH900. My music library consists mostly of rock & metal, with some pop and electronic music in the mix; most of them are 320kbs mp3 and some FLACs.
My goal setup would be HRT MSII+ > Lovely Cube DIY amp > TH900, and for portable use Astell & Kern AK100 > TH900. Is there any sense in this?
Don't know about the desktop amps but your choice of TH900 as the only HP makes eminent sense, especially with those genres.