Interesting observations so far guys. I'm debating if I need a closed headphones anymore. I own the HD800 modded and have been super happy with them given I have several great amps to power them with. For instance, my HD800 + Brack Dragon + ECP DSHA-4/L3 is nearly neck to neck with my SR009 system. Bass quantity is really not a problem for me with the HD800 either. I may have to buy one from Cruthfield and live with them for couple of weeks and find it out for myself. I suspect that those extra bottom end will come in handy when I power them portably out of my Sony NW-WM1Z/ZX300. I generally prefer clarity and transparent sound over bass thumping of the Z1R...so the HD820 may fit the bill. Still, the HD820 are more than twice the price of the HD820 and three time the price of beat up HD800. For your viewing pleasure, the very best amp for the HD800 for me thus far, the ECP L3.