Low watt tube amps/pros/cons

300B's, 845's and others. What are some of the benifits of these tubes as well as the limitations. I see someone posted that he has a 15 watt tube amp and wants to get 30hz bass. It is highly unlikely that his amp will deliver as low as 30hz, even if he did find a speaker that went to that level, would the bass have any authority? Also by saying I want to find a speaker that goes to 30hz hows the mids anf highs. IOW I'd never buy any speaker based on the fact that it goes to 25hz, its a package deal.
Back to the main idea here. Can anyone give a list of +'s and the ='s of the low watt tube amps. For myself its not something I'm interested in as all my listenings are classical, and I want the orchestras to sound full rich, dynamic, that is the low and high end extended. I heard a 300B amp, the Cayin, and was incredible with light jazz, blues, but for classical orchestral it fell flat and lifeless. The speakers were the Silverline Sonatas.