I went through quite a bit of reading up, listening and asking around about powered monitors.
My short list: Airmotivs, JBL LSR, Event BAS20/20. I found that the JBLs seemed to fit my needs better and I think they are the best bang-for-the-buck out there, the prices have recently dropped to $150 for the 5" and $250 for the 8".
The KRKs are good, but I think the JBLs are just a step above. If you are concerned about budget or just want computer speakers, then the KRKs will fit the bill and save a few bucks. If you want the next step up or are serious about recording or mixing, then I would step up to the JBLs.
Now, the higher up KRK 10-3 might be worth considering. It is a 3-way monitor, don't see that too often, but those are BIG!