I did exactly that, using the DIY kit, and am very pleased with the outcome. I put in one of these: http://www.ebay.com/itm/NEW-Aluminum-Project-Box-Enclosure-Case-Electronic-DIY-18-5x45x110mm-/161492609326?pt=LH_DefaultDomain_0&hash=item2599b5a92e The LED being blue was a bit bright so swapped...

The D2 actually sounds better with high impedance phones, because it overcomes the bass roll-off. It will easily drive my 80 ohm DT770 Pros. It is improved in detail and soundstage with the E5 added, however. 32 ohm phones are no problem.

Am this moment listening to my D2 (with the D2+firmware) connected to my E5 and Head Direct RE2s. It is very fine sound. The E5 works very well with the D2 and does in fact improve soundstage and detail. I find it makes the most difference with my best phones--Beyerdynamic DT 770 pro 80 ohm, but...

Got my RE2's yesterday and am already liking them a lot. Midrange is extraordinary already, bass coming along as they burn in. Using them with my Cowon D2 (with D2+firmware and BBE+ set at 1, everything else flat) and E5 (also flat, the bass boost sounds muddy) Clarity and detail are good...