I've now tried the AKG K 701s playing 320kbit AAC through my Macbook connected to a Marantz SR7500 (7.1 receiver), by Toslink, but haven't compared that setup to anything else. I've also listened to the phones directly connected to the Macbook. The sound isn't exactly overwhelming but on the other hand it's not unlistenable, wich is nice. It's a bit more punch through the receiver but the sound is not very clean, smooth. I've also listened to my dvd-player, wich is a cheap Philips, digitally connected to the receiver and the sound from that setup is worse than the others. Much too harsh and aggressivly sounding, also a bit tinny in the midrange. the best result is Mabook-Toslink-Marantz. I think I'll get a better result from a dedicated (good) phone-amp though, but I haven't had a chance to compare. I have heard the 701s with a Heed but that was in a store and I only compared it to other dedicated phoneamps.