YoniTubulIt will drive it decent and sound good, but the hd6xx needs about 300mw @300ohms to be driven to it's absolute best.
Still will sound good though I can guarantee it. I enjoyed my hd650s out of a mere 40 dollar SMSL amp for a long time, even when they weren't being given THAT much power. But the difference is quite noticeable, slightly in soundstage, more in impact.
EDIT: You said the AKG k7xx not 6xx. It will drive k7xx fine.