Re: Tube rings...
Some of the tube guru's say they may help some if your using a combo amp, but don't feel they are necessary on a head/cab situation.
I use them in my 2x12 combo, don't really know if they have helped, but I don't think they hurt either. I just use the cheap silicon rings you get at the hardware store, or off of ebay in sets.
Myles Rose (groove tubes, Dr Z, Music player forum) says rubber bands will do just as well, and the high-priced ones are most likely indiscernible from rubber bands. I don't think they extend tube life or anything, but probably do cut down some on mechanical noise/microphonics in combo amps.