Behringer ones are whack. Really whack.
After about half an hour your ears will be ringing and after about two hours you will have blown them up...

I know 3 people that went against my advice and bought a pair, 2 of them blew thiers up and one is just pissed off that he ever bought them.

I recently sold my KRK K-roks on ebay and they only went for £80!! if you can get a pair of KRK's at that price i would say dont hesitate. You'll need an amp though but a samson 260 will do fine (about £90 SH)

Ive recently moved to Fostex PM-2's and while they get a little ear-grating at very high volume (they are loud bastards though) i think they are excellent and my mixes have been coming out much cleaner since using them. For £500 you cant go wrong.

On a budget id look for some second hand K-ROKs..

There is nothing else that compares at even double the price i sold the KRKs for....