Hello, I have played with both the IDA-8 and 16. It will work fine with the KEF. I have also played with other amps that NuPrime makes. I can say that the STA-9, even with just higher specs, sounds a lot better. If you were to hear the 8 against the 16 or STA-9, you would hear a major difference in dynamics. It's not speculative or subjective - it's extraordinary. Also, the 16 and STA-9 just seem to control the bass much better. My Ruby speaker, a 5 1/2" two-way sounds good with the IDA-8, but listen with the IDA-8 or STA-9 amp and it makes the IDA-8 sound anemic.
Hope this isn't too direct. I am a HUGE fan of NuPrime gear and use it for reference and testing of products. My personal system at home has all NuPrime amps. In my opinion, it's easy to compare their quality with components many times the price.