I won't be using the AKG K240DF, they were just borrowed for a few days. And since the response should be as flat as possible (I don't know what you mean by transparent) isn't almost no bass equally as bad as too much bass? Could the lack of bass on the K240DF be because I wan't using an amp, or does it just boost the volume? And would DACs (such as a Focusrite Scarlett 2i4 or Native Instruments Komplete Audio 6) be a replacemnt for an amp? Or do DACs not have amps and you have to use an amp anyway? I really don't want something that's bad for me, I'm just confused because this guy from the studio uses the DT-770 (along with the K240DF), another guy that was online on a chat on a online music store told be the Beyer DT-770 Pro are best monitoring headphones under 200€, Stephen Swartz (a great but not too famous producer) uses them while sometimes switching to monitors... I'm not saying that I believe the other guys that tell me the DT-770 or that Stephen Swartz's suggestion (I chatted with him) would make me choose the DT-770, but this stuff just confuses me. I really want the best I can get for monitoring/mixing/mastering purposes in this price range.
This graph shows flat FR, try to get some hps headphones with a similar graph that are not over emphasize the bass. You can try the K-240MKII @ 55 Ohms at guitar center. I don't know the KRK, or the Sure hps, but you probably can compare them as well at your local music store.