Two developments you should know about; I'm currently trying one:
Voltsecond's "cathode mod" being discussed on the Bottlehead Forum and available at his site:
http://www.siteswithstyle.com/VoltSecond/index.html
and the TJ Meshplates 2.5v variant on a 300B envelope output tube.
Garland has tried the "cathode mod" and can speak to that. I just recieved the TJ's today. After that first hour they still sound more detailed, upfront but somehow still sweeter than the stock Valve Arts. Need some more break-in but I'm sure I'm going to miss that blue glow.Voltsecond, as you will see, has other Paramour mods and the Bottlehead Forum discuses everything from iron and choke upgrades to simply putting a cap on the mains line switch.
Spend a little money, have a boatload of fun.