I had the original Eversolo Master A6 with LHY linear power supply, the Gen2 Master A6 and the A8 (sold or returned them all). The Eversolo T8 is much better as a streamer than the other Eversolo models - in every regard including a decent built in linear power supply instead of the faulty one in the A6 Gen2.
Lumin U2 is on another lever from Eversolo for build quality and sound refinement (for more money as others have said). But you need a system that can resolve that difference otherwise there is no need to pay more.
Not knowing everyone's financial situation I would say upgrade to the T8 first. If you are going to spend Lumin money (or other high end brand) I would recommend to actually listened to it first.

