That was my Zana at the Chicago meet and I was equally impressed with the K340's. So much so that like Ryan, I'm in pursuit of a stock pair to send to Larry. The pair in question were morphsci's and they did sound awesome. And as for power needed, I was surprised. Using RS-1's on the Zana I rarely turn the volume past about 9 - 10 o'clock, with Senn's 10 - 11. The K340's were usually above 12-1 o'clock to get them to a decent listening level.
The bass was very good, but what I was impressed with was the overall balance and clean midrange on Jim's pair. They really hit the sweet spot of how I like my music.