gary_cI agree with more or less everything in this paragraph. I haven't much experience with the older Response or Studio range, but owned a pair of Response D30Rs for nearly five years. They performed very well and I had no complaints or issues with them, but last November I traded them in for a pair of K6s. As rsypder said above:
For anyone contemplating ProAc, one of their strengths is imaging (very spatial, almost holographic), but they can be fussy with pairing of electronics and cables. The good thing as well as the bad thing about them is that they will show the faults of everything else in your system, but I like that characteristic. Some people may feel it’s because they’re not as balanced or neutral as other brands, but I feel it’s because they are revealing and I find that a good trait. And although they may sound warm in some respects, they can also sound forward. But I've found that I prefer this quality, because they sound good at lower volumes (the D38 also plays loud just fine).
The K-6 was in sound a completely different speaker from the bass up. Completely and seemlessly coherent/balanced. Also, I have yet to hear a speaker with a footprint as small as the K-6 that goes as deep, full and controlled in the bottom end.I had also upgraded my CD player two months previously (to a Metronome CDt-8 S), but my pre- and power amps remained the same. Well, the long and the short of it is that the K6s were able to demonstrate a great deal more of my system's strengths (and possibly weaknesses too) than the D30Rs - and, as mentioned, I never knew the latter to be caught napping. I was considering upgrading the amps too, but after a month or so with the K6s properly broken in I changed my mind. Just like some of us here are proud of '90s speakers till today, I can recommend with full confidence the K6s, which may well stay in my system for the next 15 years ... though I hear there is a new version, the K6 Signature, out this month. At the Bristol Hi-Fi Show they were listed at five pounds short of £20,000.
In case anyone wonders why I didn't get the K8s, 1) they would have been too large and powerful for my room, and 2) they were far beyond my budget anyway.