i want to do all new tubes in my 80's ampeg svt. i know dont replace it if it aint broke, but the power tubes are like 15 years old. a tech recommended me sed winged c, but they are super expensive, like $350 for sextet. he also recommended me chinesse power tubes, but he didnt mention a brand. i just want tubes that last. i know tubes make subtle changes in tone but an svt will sound like an svt regardless. would i be ok with the sovtek 6550we, jj 6550, or tung-sol 6550? which ones have the best rep? i just want quality tubes that last and dont cost so damn much. the other tubes are 6c4, 12ax7, 12ax7, 12ax7a, 12ax7 12ax7 12bh7 12bh7 is the 12ax7 different from 12ax7a? what brand for pre amp tubes do you recommend?