I find that every tube in the TORII makes a notable difference, from regulators, to rectifiers, to power, and inputs. And different combinations therein sound pretty different, some combinations reaching an amazing synergy and stimulating amazing musical involvement. But this many choices can potentially be a labyrinth too.
So I also agree that the stock tubes will sound good, and they will give you a frame of reference, which is important. Tubes have subtle but potentially profound differences if you know what I mean, and finally choices are dependent on your system, room, synergy of it all, and the resulting tastes you develop around the sound you like best.
So if you start from a known, it is easier to determine what direction to point to for changes. And the Decware tubes are well chosen for synergy and warrantied for a long enough time for them to burn in (in the unlikely event of early failure). Then you can get a good taste of them and know better what direction you might want to go if changing tubes becomes compelling.
I have done a lot of tube exploration and really enjoy it. It is all in the quest for the ultimate involvement with the music, and certain tubes sound particularly good with some tubes and less so with others. So finally, getting just the right synergy for my tastes reveals the music in ways that satisfy me most. And with a good selection of tubes, I can shift this any time I want. Each combination then reveals the music a little differently... This can be really exciting for me. By changing it up a bit, the shift affects the mind/body response and therefore how I enjoy the music...a shift of equally satisfying quality making the music suck me in a different way and keeping my interest peaked.
Lots of folks get over rolling though, another good reason to hang with Steve's choices at least for a while until you get to know your new music system.