the 2.2 is a bit sweeter thanks to some careful parts selection (hi fi fuse & furutech gold IEC), but the 2.1 is a bit more dynamic (thanks to 2 trannys).
i'd think upgrading tubes (1 & 3) or coupling caps would be the best thing you could do.
i'd think upgrading tubes (1 & 3) or coupling caps would be the best thing you could do.