AMR DPP-777 DAC tubes

This might not be, strictly speaking, a "digital" question, but I've read quite a few threads about the merits (or non-merits) of different tubes in various components and their effect on the sound. Opinions seem to be all over the place and for a non-technical person like me, a lot of the discussion goes over my head. I have an Abbingdon Music Research DPP-777 DAC (original version, not the SE version) with its original tubes, and it's had quite a bit of use in the 3 years I've owned it. It still sounds extremely good, but I'm wondering if there would be a noticeable improvement if these tubes were replaced with, for lack of a better way to express it, better ones. The tubes are 6N11, and I don't know who the manufacturer was. Is it worth my while to pursue this as an affordable upgrade path? Thanks for your opinions.