Major Questions Concerning Tube Amps..??

I have read quite a bite about tube amps, positive as well as negative. Here are my questions. I have heard that the distortion level with tube amps are high, is this true.?? Tube amps are usually rated very low in terms of wattage, does this mean they provide more current that solid state amps and if so wouldn't that shorten the life of the tubes. If I replaced the amp that I have for my mains with a tube amp, will this drastically affect the sound of my HT being that the rears and surrounds are powered by a solid state amp.??

DMH