I can't really help - but I can tell you of all the valve amps I've used, that the things only usually start sounding really good when they've warmed up for 20 mins or so.
So I'm surprised that you're finding it the other way round? I'd be guessing there's something wrong, but I wouldn't know what...
Or perhaps you don't actually like the sound the amp's designed to give off when it's cooking? I have read that the TT isn't everyone's cup of tea. I guess it all depends on what "really cr@ppy" actually sounds like (I've heard some apparently fine tones that I think are awful, and vice versa, one man's meat and all that .... :lol:)
You'll still need one of the amp experts though...