I wouldn't bother with OP470s for headphone driving, they have a pretty wimpy output stage if OP471 results are any indication. Results with a 2-stage buffer could be good though.
Try building "the wire" headphone amp. It's almost straight from the lme49600 datasheet. I have one integrated into my dac board design and it sounds great
did this years ago with a single single NE5532 run off a 9V battery driving AKG240s (600 ohm) - worked fine, quality was good but I would have liked a touch more volume - probably saved my hearing.
