For true plug and play tube amps, I'll ante up with Audio Valve. Starting with the Avalons ($4500 for the pair of monoblocks), they include red and green LED's that tell you when a tube is going bad and needs to be changed. They are fully auto-biased, the tubes are easily accessible (by unscrewing 4 thumbscrews that hold the glass tops in place), and they sound great to boot. I have the ppp45's and I couldn't be happier with the sound or the maintenance-free life.
Michael
Michael