here´s an update (edited due to much vagueness) to anyone who might follow up on this thread in the future with a similar question.
after an appropriate burn in i´m enjoying the ef2 with NOS Raytheon 6AK5 tubes/akg701.
you will need to pay attention to your source, in this case, what kind of music files you will use on your computer. mp3 files sound ok but they force you to turn the volume to the highest position just to get a decent sound. i tried converting my cd´s to flac and that worked very well.
regarding volume (as there is the concern with akg´s that you won´t get enough volume out of them). with the flac files playing through Cog as the music player on a powerbook laptop (had to switch computers)... at 11 o clock, great background, not much detail. at 12 to 2 o clock, great for attentive listening. 3 to 4 oclock detail really comes out, but can be a strain on the ears depending on the music. you´ll really hear static in the bass area if the recording is older.
i do notice at times a certain muddiness in the music, or that the instruments seem set to far back. at other times there´s just the tiniest hint of a tinny sound in an instrument. it´s not a deal breaker, and it could be for some unknown reason other than the amp, but i assume that´s the cost of going the budget route.
through a cd player (i tried a marantz cc3000) it sounds almost as good, but lacking a degree of smoothness. an external dac would really improve the sound.
again, if you are following this post, considering on getting a cheaper, budget solution for your akg´s. this has worked for me. of course, in some years i will aim for the dacmagic coupled with heed canamp as i´m sure i haven´t fully realized the potential of these phones. but am very happy with my more humble set up for now.
best
robert