The AKG K702 are superb headphones, among the best you can buy. You will find them highly recommended across virtually all high end headphone reviews. The goal of these headphones is to play the music exactly as it was recorded without any coloration and that is exactly what they do. If you want accentuated bass for example, these are not the headphones to get-look at something like Dr. Dre Beats instead. Get these headphones because you want to hear every lovely detail and nuance that was recorded, exactly as it was recorded.
As with most of the highest rated headphones, these are "open back" so that you will hear loud sounds in the room around you and if you are listening loudly, those around you can hear sound from the headphones. If these are issues for you, consider "closed back" headphones. Closed back headphones are likely to have more coloration however due to the acoustics of their enclosed space.
Also, if you want to listen to the AKG K702s loudly, you will likely need a headphone amp (e.g. NuForce uDac-2 for $129). These are relatively inefficient headphones and require more power to be driven loudly.
Also, as noted before, these headphones will play every detail of exactly what is fed to them which means "garbage in, garbage out". It would be painful to listen to 128 kbs mp3s for example. Also, many computer sound cards degrade the sound quality of the original source material. A solution is to use a high performance "digital audio converter (DAC)" which the NuForce mentioned above also is. The DAC takes the signal via USB and bypasses your sound card. (the NuForce is also powered by the USB connection).
Note that these headphones, like most high end headphones, require "break-in". They sound great out of the box but it will take about 100 hours of varied listening before their full potential is realized.
Finally, the AKG K702s do not come with a case. You'll want to figure out a good way to store these beautifully engineered headphones when you are not enjoying some of the most accurate, lifelike sound possible.