Hmm, I know I had the answer to this one around somewhere, but...
Oh, that's right, I PUT JUST ABOUT EVERY ANSWER TO EVERY QUESTION LIKE THIS THAT I COULD THINK OF IN A FAQ THAT HAS BEEN STICKIED IN PRODUCTION TIPS.
Oh well... I guess if you can't be bothered to look for things, we'll never know... I'd go off and throw a fit, but seeing as how you either can't or don't want to look through the first few lines of a forum I doubt it would be useful anyway, so if you must be scolded for this foolishness I'll just copy-and-paste something from another thread.
As for the DI box... completely unnecessary. A DI box eats an unbalanced high impedance signal and shits out a balanced low impedance signal. Your amp has an unbalanced input, so the switch from unbalanced to balanced is irrelevant to you; the signal after a TS, which has an output buffer designed just for this sort of thing, has a low enough impedance so that you don't need one with the TS.
I won't go any more into TS stuff, because there's a bloody FAQ just made for that, and if you won't go through the trouble of reading it I don't see why anyone should be bothered to spoon-feed you things you shouldn't even have to ask (unless you don't know how a search function works), but as far as DIs go... just don't worry about them. They just lower impedance and balance signals, so seeing as how you'll most likely have a pedal or two and tube amps have high input impedances you won't need one. I'll have a FAQ on impedance up sooner or later, if there are enough people willing to click on links and actually read about things like that.
Jeff