Quicksilver amps are a great match with vintage Klipsch horn-loaded speakers IMO. I have LaScala's and Heresy's, and have also owned two sets of Forte II's. Of those the LaScala's are my favorites (same drivers as your Khorns, different housing) and I run those with Quicksilver 300B SET's (prototypes). I've also run Klipsch speakers with Quicksilver's Silver 90's (Pentodes), Mini-Mites (push/pulls), and another prototype set of EL34 Triodes made by Quicksilver. I prefer the triode combination with horns. The Pentodes were a bit too punchy for my tastes (still very nice amps), while the Mini-Mites are great little amps and a good compromise between punch and air. With the efficiency of your Khorns you can drive them with a smouldering match so power is really not much of an issue. I'd say a whole lot would depend on what kind of music you like to listen to. If you're into rock and roll and more dynamic material, go for punchy (though I wouldn't recommend SS - Bob_Bundus and I were just contributing our difference of opinion on this very subject in a recent thread on Klipschorns under the review section if you care to look it up). I've never heard that combination sound very good, but then again I haven't had that much exposure to variations on that theme. Bob's experiences have been different from mine, and he seems to like that combination very much, so I have no doubt that some may prefer it, but I have yet to hear it sound good to my ears. If you can swing the $5800 price tag Mike Sanders new 6C33C based amps, "The Triode", would likely be magic with your Khorns. They are not on his site but are available now. My friend back east uses them and tells me they are the best he's heard with his Klipschorns.
As far as a tube pre-amp, I do like my very simple Cary SLP-50A with my LaScala's and SET's. It works great for me, and is a real sleeper of a pre. It is a 2-tube linestage using two 6CG7's. The SLP-50B uses the more popular 6DJ8 family. I tried one for about a month with all forms of premium tubes and ended up selling it and sticking with the SLP-50a....it just sounded better in my system. I've found the ARC LS-2b (GNS modified) that I own to be too analytical sounding for the SET/horn combination while the Cary seems to let it 'breath' better. The ARC sounds good with the Push/Pull Mini-Mites though. Synergy.
Just my .02 cents.
Marco