I will have to also agree with Tvad's post;It has been my experience that going the pre amp route will only give you a peek into the tube world.
If you really want the whole experience I would go with tube
power amps(s);as far as the last part of your question of power with 91 db speakers I would think you would not need massive amounts of power however; I think the answer to this question is more of a personal choice; remember you may not keep those speakers forever and having a higher powered amp may give you more options when the time comes.
If you really want the whole experience I would go with tube
power amps(s);as far as the last part of your question of power with 91 db speakers I would think you would not need massive amounts of power however; I think the answer to this question is more of a personal choice; remember you may not keep those speakers forever and having a higher powered amp may give you more options when the time comes.