So much personal preference here that it's hard to recommend. The Wharfedale 8s get mostly good press here, and one of the most interesting magazine "blind shoot-outs" (conducted by a group of pros) I've seen, in Future Music mag early this year, rated the following highly if I recall correctly:
yamaha 3 and 5 models (best overall, and a surprise to the judges)
event 5 and m-audio bx5 (good accuracy)
I haven't used the KRKs, but I do know that my BX5s work beautifully for me: my mixes have never translated better to other systems, and that's the bottom line in my book. I do think that a sub, even a cheapie, is necessary with the BX5s--and probably with most speakers of that small size. Before I added a cheap Wharfedale sub, I spent too much time guessing about the low end. Now, I can trust what I hear from my monitor setup.
But again, I really think one needs to hear these monitors, or better yet, buy a few and try them in one's own home before deciding. It worked for me. Every studio space sounds different, and every pair of ears has different preferences.
Good luck,
J.