Good to hear that. What about your K701 and GS1000? My current amp has actually pretty good synergy with Senns too, but with K501 it sounds OK-ish , but nothing spectacular. I want to try decent solid state amp and it should spec wise have the power output that my AKG needs.
I use Brian Bromberg's "Cantaloupe Island" (Downright Upright, Artistry Music, 2.20.07) to test sub bass and bass, roughly 40-250 Hz, and with the HD800 I can clearly hear the bass strings vibrating. With the GS1K and K701, I hear the bass sounds but not the actual string vibes.
Also, the GS1K colors the bass, and the initial impression is that it may be better than the 800 in this range. But on closer listening, it's clear that it's coloration.