As I was searching for a good amp/ dac, I decided to save myself the trouble of picking between numerous options and get an O2 amp/ dac. Now I have to choose between JDS Lab variant and the EHP variant. I can only see the rear view of the former (http://www.jdslabs.com/item.php?fetchitem=39) and the latter seems smaller than I thought (http://epiphany-acoustics.co.uk/wp-content/uploads/2012/04/Epiphany-Acoustics-EHP-O2-Reflection2.jpg). Why is it that the EHP variant is187 dollars and the JDS LAB variant is 285 dollars? P.S. Do I need an AC adapter for both? I would appreciate it if you guys can help me choose.