What's to prefer; tube preamp or tube amp?

I'm talking stators here and I think I need BOTH tubed, preamps and amps, I've lived with Gryphons a long time, Kirk, The Ref. Mono 1 and the Electra, however with electrostats they are easily bettered both in speed, soundstage and transparency by every Spectral preamp and amp that I've tried. So for me, if not tubes and preferably Jadis, Spectral is my SS choice. I would also start with a tube pre and later try a tube amp. You should however, if driving a SS amp with a tube pre see to it, that the impedances match, which with modern tube preamps should not be too big a problem.

I found tube gear adds more life to the music.
As far as integrated goes, it works but can be better.
Seperate power source usually works better. You get better dynamic and less heat issue with preamp+amp combo.

From Tube FAQ,
" Tube is a totally mechanical device, inside a tube is just some metal plate arrangements, the effective operation area is much much larger than a semiconductor (sometimes even 1,000,000 times larger). When music signal pass through a very small area, it will implies certain squeeze feeling to the signal itself and it is very noticeable , so when a signal just pass through one transistor, you will immediate sense the compressed , flattened and hardened feeling from the music. The more the transistors in the circuit, the lesser the easiness more and more flatness and hardness to the music. "

don't forget that tubes in a preamp last longer than an amp, so the cost of replacing tubes is more efficient in the long run.