I have a some experience with both vintage Klipsch speakers and Quicksilver products. I've owned four different sets of Quicksilver Mono amps and currently use a set in each of my systems, as well as much expereince with vintage Klipsch Heritage series and their Forte II's. I'm currently running slightly modified LaScala's in my home system (reference) and slightly modified Heresy's in my work system. The LaScala's are 77's while the Heresy's are early 80's (both using the K55V with metal horns). I'm a big fan of both Mike Sanders products as well as the Heritage line of Klipsch. Although the Heresy's are probably the least appealing of that line, they still are cabable of big bang for the buck considering a pair in great shape will cost you about $400. I do think they mate well with tubes. As far as creating a "lifelike 3-D soundstage" I'd have to conditionally agree with Gthrush1: they are cabable of a very nice transparent sound, but there are better speakers. Still I do think they are very impressive considering their price. There are some very simple tweaks you can do to improve their sound. I found the stock Heresy to have a slightly forward/harsh midrange and highs, partly due to a lack of bass I think (I'm referring to the Heresy I with the E crossover and NOT the Heresy II which I have no experience with). I just recently did a whole bunch of experimenting with various tweaks to address this problem and managed to get them to sound a whole lot better (more balanced sounding) with only a few easy steps. I just outlined exactly what I did on the Klipsch forum page so I will cut and paste that here as it goes through the entire process I went through. The improvement is significant, though certainly not night-and-day, I would highly recommend the tweaks I ended up with. The overall results are a more balanced and less fatiguing sound over long range of listening. There are several threads on the Klipsch forum that do outline many folks attempts at tweaking the Heresy's. Most echo the sentiment that the Heresy's are pretty darn good as they are, and it doesn't take much to bring them to optimum performance. I mate mine with the 25 watt Quicksilver Mini-Mites running vintage Tesla EL34's. They are certainly not as holographic as the combination of 300B SET amps and LaScala's that I run in my home system, but the combination of Mini-mites and Heresy's with the mods I recently completed is eminently satisfying and non-fatiguing. 25 watts of tube power is plenty for the Heresy's and I'm listening in a VERY large space (1300 SF with 11 foot ceilings). No need for 100 watts IMO. I haven't heard the Quicksilver 100's but I did own a pair of his Silver 90's (KT88 based pentode monos). They were great amps if you prefer listening to punchy rock-and-roll, but he makes better more refined amps that suit my tastes which range more into acoustical, vocal and classical. OK, so I won't waste the bandwidth here to paste the entire thread from the Klipsch forum that outlines the mods, but will provide two links. One will be to the thread I started recently there which outlines my steps and the mods I ended up liking so much, and the second will be to an earlier thread on the same forum that outlines what I think was the most significant part of my mod, a very minor alteration to the crossover. I reference this thread in my posts to the forum as well:This is the thread I startedAnd this one is a thread I referred to with the crossover mod
Originally with the Heresy's + Mini-Mites I thought it was a good combination, but ultimately was a bit fatiguing on long listening sessions (yes, "nothing special" in that regard). With the mods in place I am much happier with the combination and it is one I can live with happily in my work system. Were it my reference system I may be inclined to move on to further improve the sound at some point, but for the money I think the combination is outstanding.
Hope that helps.