tubes and rock and roll, good fit?

Consider how many rock musicians/bands use tube amps. Any other questions?

Of course they will work but as others stated, most important is the match with your speakers. I'm not a fan of Krell, but then I only owned their amps/pre once. They offer good bass control (again depending on speaker match) but don't offer enough communication of the musical emotion for my taste. YMMV. I did own VTL 300 monos for a number of years and found them to be a great middle ground with characteristics of both tube (emotion, warmth, dimensionality) and SS (bass control, detail, clarity).

Pryso, I think musicians/bands often use tube amps as a means of introducing distortion in a controlled manner which is easier achieved with tubes than SS.

Same is true with use of tubes in home audio gear, but the goals of the listener of a home system is generally to avoid certain distortions, not apply it, which is different. BOth tubes and SS can accomplish this if done properly, whereas tubes are much better suited for introducing distortion into an electric guitar, etc.

R&R musicians are driving intrument amps and PA systems.

I'd give serious consideration to VAC's new Statement 440 amps. I chose VAC (Phi 200) over VTL (MB 450sII) because I found more musicality, better control over microdynamics, and all around more lifelike sound from VAC.

That being said, Gryphon is what Andy uses, a point you should not overlook.

Musicians use tubes because of their musical overload capabilities.

If you really want to try out a tube amplifier, and see it rock out properly, the first thing to understand is that tube power is more expensive than solid state. The second thing to understand is that (with transformer-coupled tube amps at least) the bigger the amp the less bandwidth, due to limitations of the output transformers. Rock, like all other forms of music, demands bandwidth!

So the speaker is the real issue: in the world of tubes, there are two critical variables: impedance and efficiency. Low impedance low efficiency speakers are popular today because 600-watt transistor amps abound, but such are anathema for tubes **if you really want to hear what they do**.

So I recommend a speaker that is at least 8 ohms, and efficiency that is at least 90db. That way, you will be able to achieve satisfying rock in most average rooms with about 200 watts or so. Keep in mind that for each 3db of increased efficiency is the same as doubling your amplifier power- that is why in the industry amplifier power is often referred to as 'gold plated decibels'. If your speaker is only 87db, you will need a prodigious amount of power (+400 W) to make it fly, and its just simple physics that tube amplifier output transformers will not be full bandwidth at those power levels.

The speakers I run (since I play lots of rock and I'm pretty demanding, regardless of the music) are 97 db and go down to 20Hz so I can shake the walls with only 60 watts. Yet at the same time these speakers are as revealing as the best ESLs, IOW I'm not sacrificing any musicality for the increased efficiency- rather it seems to me that most lower-efficiency speakers are the ones sacrificing musicality for their lower efficiency...