help on tubes

howdy Audiogoners, i just got myself into tube amplifier.as of right now i dont think i would go back to SS again,therefore i need to learn about tubes so i can purchase the tubes replacement for my BAT vk60. my question is..is there a website for me to read and learn about the differences of tubes ?or Can some 1 recomend to me what kind of tube is best for my Bat.i have no knowledge about those tubes on top of my amplifier at all..please help...