while most wouldnt consider M-Audio to be a good speaker brand, their monitors are actually REALLY good!
back a couple of years ago when I was looking at monitors, the KRK RP-6 was heavily pushed as something I should check out and honestly, I didnt like their sound. the high end was very thin and brittle sounding (to my ears) and the lows left something to be desired.
after spending several hours in various Guitar Center, Sam Ash and other local music/instrument shops with cds I knew well I went for the M-Audio Studiophile LX-4 series and couldnt be happier...half the price of the KRK RP-6 and sounded much better.