I loved the HD631 for bass and everything else. Superlux has some absolute gems in their catalogue. Glad to see a review of some of their gear!

Great review.  I had the original HD681 for a while.  Sold it due to the treble (wasn't good with a soldering iron for modding lol).  Another Superlux model I'd recommend is the HD662 EVO.  With some simple mods, it sounds really good.  Here is a link to a thread with instructions, graphs, analysis, etc. http://diyah.boards.net/thread/1169/superlux-hd662-evo

Excellent review, thanks

Great! Thanks.