@backwash I agree that it depends a lot on what you are looking for in an upgrade. The X1 is certainly a significant hardware upgrade and for many also a significant sonic upgrade. If you want the best-of-the-best Lumin then of course you'd go with the X1.
But if you are looking for something that would lean in a different direction, then there are lots of different options. Don't rush to replace the T2, and instead try to compare its analog output to that of other DACs to see if there is (or there is not) one that you like better.