Hi folks ... I know next to nothing about tubes, let me say that right off the bat. I have a Groove Tubes Trio preamp, which is a nice little piece with three channels. In my working band, I primarily use the Clean channel, which is a blackface Twin style circuit, designed to have nothing but headroom. GT advises running both gain and volume wide open at all times. Right now, it's very clean but a little too sterile; I'd like to warm and fatten it up a bit, maybe just a touch of overdrive available, better lows. Is there a preamp tube that is reasonably priced and easily available I might try in there? I know there are some reissue tubes being made now that are supposed to be pretty good. Not looking for expensive vintage stuff, though! Thanks!