Opinion of Quicksilver KT88 60 watt mono amps

Does anyone have experience with these amps. Does anyone know what they might be worth on the used market.
It depends on the condition of the amps and the condition of the tubes. If the tubes are either old or not matched well a replacement set of tubes will run you about $400. The price range in good condition is $800-$1,000.
There are 2 versions of these amps, the original and the II. The QS website has the manuals for each, and I believe the rectification is the difference. There is also a nice review of the original on the internet, and the consensus was that it is lacking in the nether regions, has a slightly forward midrange, and is balanced in the highs given you don't use EH power tubes (awful to my ears). I lived with the M60s (also 60W) and found that to be dead on accurate. I liked the amps, regardless; however, the guy I bought them from owns and prefers the KT88II due to its tube rectification. I would say $900 would be reasonable for a pair in very excellent shape but no more due to their age.
It's one of the most reliable and easy to maintain tube amp.
One could be compared to the units that are worth 4...5x the price paid.
I own a pair of Quicksilver monoblocks, and have to say their level of refinement far exceeded my expectations.

Echoing what Marakanetz said, with brands like Quicksilver, why would anyone pay more money for the inferior Chinese imports? You deal with a good company, making good product, providing good service, get to enjoy not only good sound, but have some pride of ownership, and if the time comes to move on, there will be demand from buyers.

From what I see, M60 pricing ranges from $700 - $1200, depending on condition, etc.
I was asking about the KT88 Monos, which are 60 watt, not the M60 which uses EL34 tubes. The original price on KT88 was about $1895, for the M60 about $1995. I assume they sound different from each other.
I am a SS man but if I were to get a tube amp it would be a Quicksilver based on their long track record and high quality at a reasonable price.
Don't bother. I had a pair back in the early 1990s. If you want 1950s sound, buy them. Poor bass performance. Mid range is nice and highs are a bit rolled off. The stock Chinese KT88 back in the day were junk. I pitched them and replaced them with US made 6550. The GE version was robust, the smaller Sylvania sounded like the original US Tung-Sol, but the Tung-Sol was the best sonically and would last forever in the amps. The amps are not hard on good tubes, and a well made 6550 will work great in them. I had the model that used two 5AR4 on each amp. That is the model you want - if you must get them. While I am not a big fan of the "audio experts" for the "big mags", I will admit that Dick Osler's review in Stereophile (back in the day) was spot-on the mark. Read it before you buy a pair. Just remember this, you are basically buying an amp design from the 1950's. Nothing that special, but they are musical and with good tubes, are very reliable.
Robetozian, what currently available tube amps are not based on a '50s circuit design? I thought most advancements have come from better parts availability, not new designs. I'm asking about tube amps in general, not just Quicksilver.
Tube amplifier circuits have`nt change very much(no need to).Refinement, better power supplies and high quality parts will bring out the very best of these classic circuits. There are many current tube amps with good to excellent bass performance available.Don`t forget transformer quality matters quite a bit.
I agree if there's mid-60's circuit you're lucky:)
Quickies and HH Scott are the most advanced tube amps so far.