Frst of all, I'd consider realigning your assumptions. Right, that sounded awful, put it this way: if you're hearing a wonderful difference, for god's sake man, don't fight it. Computer for digital transport plus an outboard DAC can sound fantastic. Full stop. If you think that is the case, it is. (And not knowing what you're comparing it to, that's about all one can say about that.)
As for the benefits of additional tweaking from there, that's -- like all things -- debatable and indeosyncratic. For example, I demoed either Decibel or PM on my system, and found it to be a tweaky PITA with no appreciable sonic improvement. So unimpressed that I deleted it and now don't even recall which one it was. Most folks, however, will tell you that there is varying levels of improvement to be heard with other players. Up to you and how things work on your system. I'm still agnostic, exploring more is definitely still on my list, but near the bottom.
Also, there is a correspondingly raging debate regarding whether upmarket USB cables make a difference. You're well familiar with "The Cable Debate" -- which is not worth getting into -- well, no suprise, no different with USB. Only trouble, there are some differences with USB that make the whole debate different enough that, well, there's a whole new debate. I for example, am 100% in on the fact that "regular" cables (IC/Speaker) make a huge difference on my system. They just do, deal with it. For USB, though, I have not found that to be the case (went from stock computer cable to a $300-ish all-silver-audiophile-approved iteration and heard zero difference). Again, YMMV. Personally, spending more on USB cables is no longer on my list at all.
I have heard speculated elsewhere, that the comparative lack of improvement I experienced with both players and USB cables may -- to some extent -- be a factor of the tech (asynchronus USB interface) used in my DAC. Just so you know, the tech used in different USB DACS for clocking and such is very different (I'm on the receiving end of the proprietary asynchronus tech developed by Wavelength and licensed to Ayre). It is not going to be an apples to apples to apples comparison. Some interfaces may benefit more from changes than others. Some negligibly so. If you're not using USB, then there's a whole different set of considerations. In short, I expect that this "debate" is -- more so than other realms in which we might argue about wires -- simply so much noise for the simple fact that folks are likely talking about materially different things. Take two: what might work or not work with your DAC is irrelevant to what might work or not work with my DAC becasue we are probably talking about significantly (in the pure scientific sense) different technology. They do the same thing, yes, but they do it in different ways and thus will react differently to ancillary changes. Or, that's my theory, at any rate.
In short, if it sounds great, it sounds great. Don't fight it. If you want to keep tweaking, keep tweaking. There's always something that can be "improved" upon. If you're looking for excuses to relax and enjoy, there are plenty. If you're looking for excuses to race about after the next great improvement, there are plenty of those, too. Takes your pick, and have fun either way.
