Hmm. What is "tube" sound?Smoother and more detailed than transistor, more lower ordered harmonics which are harder for the ear to detect. Less higher orders that the ear easily detects as harshness.
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If you really really have to make a choice of which way to go, my money is on the tube preamp.
The reason is simple: I don't care how good your amp or speakers are, if the preamp looses definition, there is nothing you can do to replace it downstream. Tubes simply make more detail than transistors (and also without brightness); they are easier to listen to for hours too, so send that to your amplifier.
The problem here of course is if the amp isn't up to the task, you won't hear what the front end of the system is doing. I do regard the use of a tube preamp with solid state as a compromise.
If you really want to hear all that is on that LP or CD, get a tube amp to go with the tube preamp.
Some people think that they don't want the tube amp because of reliability or heat concerns. Tubes are easy to deal with (they are in sockets after all) and heat is a function more of what class of operation the amp employs rather than whether or not it has filaments. A solid state amp biased to the same level of class A operation will make 90% of the heat that a tube amp does. IOW, many tube amps run hotter because they are biased harder.
Transistor amps tend to be biased at very low currents; that's the main reason they make less heat.