Great sound, great features, great amp!
I bought my KB 4 as an upgrade to my aging KB 3, which I bought when this series was first introduced. I was pretty happy with the KB 3, but it was beginning to show its age, and becoming a little flaky after 8 years of use. In my new amp, I wanted one with the same feature set as the KB 3, but with a bit more oomph.
The KB 4 sounds great. The highs are nice and smooth, and the bottom end is nice and full. Overall, the tone is very well balanced. All the controls feel smooth, and the connectors are nice and tight. Typical of Peavey amps, it's built like a tank. Well placed, heavy-duty hardware makes moving the amp relatively easy, despite the weight.
I have only one "complaint" with the KB 4, which is the master effects loop. It's a stereo effects loop, with no mono switching. All of the channel inputs allow connecting mono inputs on the left channel, and like most mixers, the input is then sent to both left and right buses. The master effects loop is also stereo, but if you run a mono effects rig (like a standard pedal board), plugging into the left channel does not split out to both channels. So, when the signal is then summed to feed the power amp, the clean signal is summed with the effected one, almost negating the effects. The work-around, of course, is a "Y" cable on the effects loop return, but that's an extra cable to cause problems on a gig, and I wish that Peavey had some sort of mono-switching on the master effects loop.