BAT vs. Quicksilver

Although both are excellent products, I would probably choose the Quicksilver because of it's ability to accept a wide range of tubes.

The BAT VK-60 is capable of running ONLY the 6C33C output tube (which I dislike) and the Quicksilver is capable of using KT88, 6550, 6L6 and EL34.

The EL34 and 6L6's are at the top of my all time favorite list with KT 88 and 6550 not far behind. There are lots of choices, with both NOS and current manufacturers offering a wide range of choices in glass, making it easy to "tune" to your speakers, power needs and personal preferences.

I will admit that the driver circuit of the BAT is potentially superior with it's multiple octals, and if you really want more power, the KT88 is the likely candidate for the Quicksilver as it produces the most power.

Any chance of hearing the Quicksilver before deciding on a swap?

unfortunately there aren't any Quicksilvers locally that I could hear. I would keep the BAT & audition the Quicksilvers. Whichever one I liked better I would keep.

There is a QS on sale today by seller thatpreviously owned by a BAT-VK-60 owner. You might be able to speak with him/her.

You may also want to consider the Quicksilver Triode, a much less publicized
unit which Sanders doesn't even have up on his website and sells by word of
mouth. It uses the same 6C33C tubes as the BAT and is built on a similar
chasis as the V4 (but is a completely different amp). Rarely seen used, I
believe the retail is around $5k for a pair so it is in a different price league. I
know at least two A'gon members who own and love these amps: Boa2 and
Jordi. Contact either or both for input on them. I have no direct experience
with them, but have owned four different pairs of Quicksilver amps and have
loved every one of them in their own right. Mike makes some damn good
products. Be aware the Mike (Quicksilver) is moving his business from Reno
to Denver over the next month, but I'm sure he will respond to any queries.
Over the years of dealing with him I've found him to be a man of tremendous
integrity who stands behind everything he makes.

Marco

As Jax2 mentioned, we do have the Quicksilver Triodes, and absolutely love them. They have a purity and musicality to them that is startling. Given that Mike Sanders does not advertise them (or any of his products, for that matter), none of the $5800 you pay for the Triodes goes to anything but materials and labor costs. In other words, Quicksilver products represent a ton of performance for the money.

Unlike Albert, I happen to love the 6C33C tube. They have a rounded, robust sound to them that I find to be quite natural. Not too exaggerated in any regard. I also like the sound of the KT88, but it does not IMO have the same depth of musicality that the 6C33C does. I don't much care for the EL34 tube either, though with music more oriented toward midrange, they can sound nice. The thing is, however, that you listen only to rock. So you're not likely to be hanging out with the midrange too often.

The Triodes would work beautifully. The V4 would work quite well, especially with the KT88 tubes. And yet, if I only listened to rock music, I personally would opt for an Audio Aero Prima Hybrid amp, which is now available (I believe) in a 100W version. I think it is under $4K, though I'm not positive about that. With the AA, you have a level of musicality that few amps approach, the warmth and emotion of tubes (it uses hard-soldered miniature tubes that are cheap and last 10,000 hours), and you will have the tight, defined bass presence that is so characteristic of solid state. If 50W is enough (probably so), you could opt for the current MKII version, which has remote. It is an amazing amp, one I have recommended to quite a few people, and they are all amazed with how good it sounds, as well as how loud it plays. I only say that because I do believe that the 50W version would do the job quite well. They can be found used for around $1300-1400.

If you listened to jazz, vocals, classical, etc., I'd have a different response. In that case, the tubes would be a slam dunk. But for rock only? The AA hybrid amp plays all genres beautifully, but is particularly stunning with rock music.
Best of luck,
Howard