I have a set of KRK Rockit 5's. I haven't really gone and done a thorough studio monitor comparison or anything amongst various brands, I just happened to find these CHEEP at an estate sale ($20!). They are quite a fantastic pair of monitors I think. I haven't done any sort of heavy-duty mixing on them just yet, I've been using them as just some bedroom speakers to listen to my music collection and run my game consoles audio through them. Listening to some of my higher-quality recordings on them is quite revealing. The frequency separation and spread on them make my existing recordings sound really good.
I've heard from recording engineers that getting to know your monitors is really what makes the difference. Whether you're mixing on a cheap set of monitors or a super high-end set, as long as you know their limitations and how to mix on them so your recordings sound good on a range of other listening environments - that's the key. Listen to some of your favorite recordings through a good stereo, some headphones, car stereo speakers, then listen to how they sound through your monitors and try to make your own mixes match THAT delta; and I think you'll be okay.