i own the 20th shiva, what an amazing and versatile amp. the clean channel is very chimey and clean, pretty much good as it gets for me... the gain channel will go all out for sure. very raw and in your face gain like stated before. and no it is not the tightest amp but plenty tight to play rock-metal for me. tighter than a rectifier for sure. and the gain will get very high. another bonus is the headshell is smaller, and not a very heavy amp (like 40lbs). one of my favorite amps. still wanting to throw some new chinese 12ax7bs in there, as i am still running the pres that the previous owner was using (a random combo), but still sounds pretty killer. pretty much everyone says these amps like the chinese pres the best. as far as the power tubes go i think it just depends what you are going for and personal pref. i like the kt88s because it keeps the clean channel very clean with more headroom, and keeps the gain more on the modern side of things. i can imagine kt77s would be badass also, and im sure el34s would be cool too. found mine on evilbay with a roadcase for a crazy low price, just FYI keep your eyes open.