Right now I am listening to my Gustard stack that comprises the U12, X10 and H10 with my HE400i's and I can't imagine how much more improvement can be realised without spending an obscene amount of money.
Perhaps we fool ourselves and imagine an improvement when we spend more money because psychologically we need/want to justify our expenditure.
I, for one, am quite happy with my gear and really can't tell much difference/improvement between my desktop dac/amp combos even though some cost quite a bit more than others. To be fair, they do sound different, but better...? who knows, not to my ears, and that's what it's all about, buy what sounds good to you, forget all the hype and the bloated price tags and just enjoy the music! After all, that's what it's all about, THE MUSIC, not the equipment.
So, try to ignore the siren song of the new/better/expensive gear and spend more on the music content as equipment will come and go but music endures and will continue to give pleasure for many more years than a piece of gear.
I love Captain Guinea Pigs' term, "Audiophilia Nervosa", it's right on the money! Bravo Captain.
Cheers from OZ and enjoy the music.