Tube Amp. Power ratings

I'm a solid state guy intrigued with tube setups....Is this like everything else in Audiophilia, Eye (or ear) of the beholder? ....Would you always have a tube pre-amp with tube amp? In general terms how do tube amps differ? Warmer?...mellower....And what about the output ratings? The tube ratings seem much lower than SS...Is that the nature of the beast?....