No experience with the 280, but I haved a Kinergertics KBA75 which I use on my Kinergetics SW800 subs. Good amp for my purposes, no reliability problems. It can also run my ML CLS's full range without breaking a sweat. While it sounds quite good on the CLS's, it is not as open and lacks the overall "magic" of my tube amps on the panels. The CLS's, like other esl's, are a real acid test for upstream gear -- for what you are likely to pay, it should be a good value relative to performance, depending on what speakers you plan to drive with it and your musical tastes. I find the amp to be neutral sounding with very good bass control, although not close to the ultimate in air and detail.
Tony Di Chiro says it runs 100% class A. Although, he did some calculations based on the impedance curves of the SW800's and swears that it will run in pure class A for these speakers, I think Sean is correct in looking at these as AB, leaning towards class A in bias. Again, I cannot compare directly to the 280 but my amp is built like a brick you-know-what. I forgot the specs that Tony gave me re: power supplies, number of rails, etc., (it has 5 or 6 fuse recepticles on the back), but it is very substantial. Mine has two internal fans that are not audible during operation. Service can be had though Fred Pham in Los Angeles,(used to work for Kinergetics and still services all products). If you buy and want contact info, just email me.
Interesting side note about the KBA 75... some yahoo who was trying to sell one here on A-Gon claimed that his KBA75 was "one of a very few" that was THX certified and designed to put out 140 watts. Pure BS, per Tony. An amp was sent to THX and was certified but it was a stock unit -- the same as all other KBA 75's. Turns out it *was* rated at 140 watts. Also, it was never designed as a 75 watt amp, as the name might indicate, but as a 100 watt piece. Tony said something to the effect that "at the time there were a lot of 100 watt amps with '100' in the model name" so he decided to do something different. Definitely marching to the beat of a different drummer, but making very good equipment for that time frame.
I recall that the KBA75's drove the mini-Statement system that took "best of show" several times in the 90's. I would guess that the 280 is cut from similar cloth. To be sure, there are better ss amps of current vintage -- less worthy performers, too.
Too bad about Kinergetics -- good designs and good products (Chiro stuff does not count), but not such good business acumin.
I've often wondered whether this amp might make a good candidate for upgraded caps and resistors. No doubt there is better stuff available than when it was built. Hmmmmm...