how would an entry-level tube system compare?

I completly agree in your point on lumping ss nad tubes into 2 piles and end of story. Each tube every lab are different, by alittle and also much. Not all tube amps are built the same, sound the same.
Also agree that its OK to listen to Rock on tubes. Johhny Winter Live And cd never sounded better, I heard details never heard before on my little Jadis, bass "rock" solid. But its not the music I prefer to play on tubes, I feel its abuse, and have no plans to buy new tubes, or risk putting pressure on the Jadis. I do not like to send off for repairs.

Thanks for all the feedback everyone.

As Bignerd100 and Tvad correctly guessed, I really do want to experiment with tubes for a variety of reasons. A lot of the music I listen to is very well produced and has many nuances that I'm expecting tubes to accentuate. Plus I'm in the mood to try something new. Plus the concept of tube-rolling appeals to the DIY-er in me. Plus 25% of the other music I listen to is tube-friendly. Plus they look cool.

Bartokfan - I wasn't aware of the wear-and-tear factor on tubes of loud, driving music. It makes sense. But I think it's a reality I'm willing to live with.

So given the <50W factor, based on all your comments it seems that high-sensitivity speakers are key. So my natural follow-up question is: how highly sensitive do I have to go? (I should qualify that my statement of wanting to shake the house was somewhat hyperbolic.) Do I need to be thinking about 100db+ sensitivity, or will 89-91db (which seems to be the sweet spot in terms of offering the largest number of options) suffice?

Thanks all...

PS Barktofan - I'd be curious to know where you see Cayin A88's for $1000 used. I'm seeing more in the $1500 used range on Audiogon. Please let me know...

Just a couple of suggestions:
1)Listen to a mid-priced horn system to see if it is to your liking. This will give you the largest performance/dollar return.
Teh problem with horns is that you like them or you don't and they have to be very large to produce deep bass.
2)No mater the design of the speaker stay above 93-94db efficency. Even 84db efficent speakers can sound wonderful with low powered tube amps for everyday listening but it is when brief peaks demand power that it will run out of juice and sound terrible.
3)Single driver, high efficency speakers can sound wonderful too. But for huge swings in dynamics they are likely to fall short.

If it is in your price range Tyler has come out with some beautiful horn-loaded speakers. Also check out Pi spekaers. You can buy them preassembled or as a kit. The guy who owns the company is very nice and accomodating. Old JBL or Klipsch should be high on your list too. Possibly Bag End PA speakers even.

Good luck!