1: Its hard for me to gauge the power difference between 30 tube watts and 30 SS watts because 30 SS watts seems a bit to light to me.
2: I wouldn't want to buy too small of an amp and be driving it hard constantly.
3: Have you had one or listened to one extensively?
4: How would you describe the sound signature?
5: What kind of equip does it like to be paired with?
6: How much is too much to pay for it?
7: How long do tubes typically last in home audio stuff?
8: Do they tend to be reliable or unreliable?
9: What are it's strengths?
10: What are its drawbacks?
1: 1 watt is 1 watt is 1 watt. There's no asterisk next to the forumlae for calculating power that requires a parameter declaring whether or not you are calculating a solid state watt or a tube watt. The real difference here is clipping. Clip a SS amp with compression drivers and you are asking for a Klipsch repair bill. Clip that Dynaco and, well, nothing happens.
2: Given that the power supply caps, rectifier, and transformers are behaving properly and the bias is reasonably close to spec, driving it too hard won't be an issue. My Heresy I's are 96 dB efficient and are 8 ohm nominal. I drive them with a 6V6 amplifier that is rated at 8 watts of power while driving an 4 ohm load. With an 8 ohm load such as the Heresys, that amplifier makes about 4 watts. I never have the volume up above the 1:00 point as it gets painfully loud.
3: Fairly so. The old old shop had one up and running with KT88's for quite a while when I hung out there regularly. Ian (vstarkwell) also has a very nice ST70 in his collection.
4: Assuming the topology of the original circuitry has not been modified, it'll vary based on your tube complement, tube condition, and the condition of the resistors and capacitors in various circuits.
5: Loudspeakers that have both high efficiency and drivers that possess a high electromechanical damping factor are always a plus for any tube amp that makes low to moderate power.
6: It depends how badly you want the amp.
7: Assuming that the amplifier is operating properly, quality manufactured tubes will last an awful long time. My Magnavox 8800 has original power tubes from 1960. I know nothing about how often the unit was used before I acquired it. All tubes tested very strong. I've run the amp at least 1-2 hours a day for the past year or so and everything is just fine.
8: As bmwr75 said, if the components on the amplifier are all operating properly and routine maintenance is not ignored, they are extremely reliable.
9: You'll fall in love with your music collection all over again.
10: You'll have a bit of parting anxiety when you sell your solid state amp.
