mixing is a complicated intricate process, as for your headphones, I have used them, and they are okay, the main thing you need to know is what is the frequency response with the equipment you are using. So that way you can understand what you are hearing, the best thing you can do is when you mix in headphones, switch back to your speakers, and listen for the difference, compare and improve, if your headphone mix sounds a lot like you speaker mix, then you've got it, unless you don't like the way your mix sounds. A good website to check out headphone frequency charts is [[url=http://[/URL]="http://www.headphon…"]HeadRoom: Stereo Headphones, Amps & DACs, Wireless, Noise Canceling, Ear Canal, Earbud, Audio Cables & Accessories[/]="http://www.headphon…"]HeadRoom: Stereo Headphones, Amps & DACs, Wireless, Noise Canceling, Ear Canal, Earbud, Audio Cables & Accessories[/], unfortunately your headphone chart is not on the website, but you should be able to get one from akg, or one should have come with your purchase.

But for mixing in general, especially when you are starting out it is good to compare your mix on various playback devices, i.e. home stereo, car, television speakers, and so forth, that way you can see how your mix translates, and keep practicing.

If you have anymore questions let me know, and I hope that helps.

For someone starting out, those are very passable tools.
My monitors and headphones are in a similar range.

My advice:
In general, you want to rely on your monitors for things like stereo imaging, balance, and overall sound.
In order to do this properly, you should spend several hours listening to recordings of bands/artists that you appreciate, and have a great deal of familiarity with. Learn what your favorite recordings sound like on your monitors. This will give you your best reference.

Second, use those headphones to check levels and balance, but beware of the stereo imaging - it will be more exaggerated in headphones.
'phones are also a good way to check the bottom end of your mixes if your monitors are lacking there.

Finally, Ravi's point about checking your mix on different speaker systems for translation is very important. Just be aware that if you pay too much attention to each system, you'll be chasing your tail fixing things that are right in one, wrong in the next. Make sure your mixes translate, but learn your main (reference) monitors first and rely on those more than others.

Hope that helps.