Local Guy, I began my Decware Journey last year with a Taboo MK III and a pair of Audeze LCD 2.2 headphones. For a long time I didn't have functioning speakers so I became very familiar with this combo. Later I added a lot more gear and three sets of speakers. I also have a pair of Sennheiser HD 800's that I find play best with my CSP-3...they are not my favorites...a bit too bright for my tastes.
I haven't listened to headphones for a longtime but plan to this Winter. I haven't listened to the hifiman headphones but really like the Audeze cans...detailed and warm. I added an aftermarket balanced cable from toxic cables, Silver Widows, that ran close to $500 but the standard cable works fine also. You can't go wrong with any of the Audeze cans in my opinion. Read the reviews and the head-fi fourms (
http://www.head-fi.org/) have tons of info and oppinons on Audeze cans, the Decware Taboo MK III and Toxic cables. Hope this helps, Mark.
PS...at head-fi I'm sure you'll find someone with both headphones you're considering. As I recall, there is one guy who has posted reviews of many, maybe 50 pairs of Cans.