[yepimonfire]

From a purely objective standpoint do the k240s need an amp with a low output impedance in order to achieve the designed frequency response? They can get plenty loud on my laptop but I don't know if their varying impedance vs frequency is enough to cause a significant variation in their response.

I'm assuming the output jack on my Acer isn't low impedance, as most cheap hp jacks aren't.

 

[PurpleAngel]

For a 55-Ohm headphone, the K240s are somewhat power hungry.
If you can get the K240, fairly loud, when plugged into your laptop, I'm not really seeing a worthwhile reason, for buying a headphone amplifier.
For the price of a decent headphone amplifier, you could sell off the K240 and buy headphones that are not really more power demanding (then the K240) and sound better.
The K240 are decent sound quality headphone, for around $100 price.
Check out the Massdrop (Sennheiser) HD58X or Massdrop (Fostex) T-X0 headphones

 

[lerian]

Be careful with those cans because they are very transparent and its very easy to damage your ears permanently playing at loud volume. I know someone who did that after only a few minutes <10 of monitoring some beats at loud volume with k240s through an amp.

I can drive mine easily with my smartphone (famous for low headphones volume) so you should be more than fine with anything else.

 

[Tsukuyomi]

Yes. next!
.
.
.
but seriously, most headphones from AKG are power hungry and ive never seen a phone/laptop/pc properly drive them without a proper amp or amp/dac combo.