I was first exposed to KRK'S when i first go into music production (through friends and what ever) and had no opinion. Now that I've learned my ears, i've found that the KRK's are kind of glorified consumer speakers. You can mix on then, but there's other things that are a little more expensive that will boost your ability to understand what's coming out of the speakers better than KRK's.
I own yamaha hs8's, and i think they're really good. These speakers will annoy the shit out of you if you don't fix something in a mix. It shows you a good deal of what's wrong and what exactly you need to fix it. They're kinda like a friend who'll point out your flaws to you, but unless you do something about it, he won't stop telling you about what you need to work on.
I'd also suggest you get some stands with what ever purchase you decide on.
