Tubes are kind of like pickups, though - "something nice" is going to vary hugely from person to person. Your best bet, barring huge reliability issues, is to just try them, and see if you like them more than what you have now.Yeah I know, just ewanted to get something nice now.
That's one of the things I find with Sovteks. They are so cheap there is no reason not to keep a spare set around in case something goes on you.Everyone's got an opinion. You just won't know if your tubes are going to die at random or not.
So grab a set, put them in, and rock out.