as you put it, there is definitely a sweet spot of quality/performance/price. haven't used the koss personally but i've had good luck with the brand and concur on the AKGs.
both will be much better than sub-$250 ear buds, comfortable, and won't need charging.
i love the retro tech trends.
@jwildeboer Just remember the difference between open back and closed back ear cups. Open back are known to sound better, however, you will also hear all the ambient sound around you. And, as mentioned in another comment, other people will hear your music.
Don't forget about Grado's too. SR80 is a good value for the cost.
And in case passive is a dealbreaker, at least the Koss headphones are available as a bluetooth version, with option for wire.
@jwildeboer Personally, while I love the design, I found Porta Pros to be uncomfortable. Therefore, In now own KPH30, but they break very quickly due to plastic design. Guess when mine break even more (they are 60% scotch tape at this point), I'll try KPH40 - but they are staid to be warmer.
But, in short: Koss is great.