The Qutest is a wonderful DAC. Regarding upgrading, with a TT2 you will get a wider, deeper and more stable soundstage (better separation) compared to the Qutest. It will be more detailed and the overall listening experience would be more immersive. I think you will find the bottom end will be fuller as well.
Is it worth it? That is a matter of opinion and very much depends on how much the incremental cost hurts your pocketbook. The TT2 is an evolution rather than a revolution in terms of sound. It is noticeably, incrementally better.