Your system good as it is. The weakest component, for me, would be your sources. I have the same Sony you have. Its OK as a back up or to just try SACD but your other components are in another league. As far as your PC setup goes, I can't comment because the sound varies so much from system to system, I could only guess as to how good it sounds. My recommendation. Get a real CD player. That will be a huge improvement. If you need other formats besides Redbook, two players I would look at are the Ayre 5 series universal and the Cary 306 CD/SACD players. They both sound incredible. The reason I choose these 2 are for Redbook. With most multi-format players, CD quality is sacrificed. Not so with these two. They can easily hold their own against Redbook only players in the same price range. And since most people have a lot more CD's than other formats, it just makes sense to have a really good CD player. (CD needs all the help it can get).
I see that you are considering things like tube rolling and new cables. I won't tell you not to do that. Its your choice. I just don't think they will come anywhere near the improvements that a new source will bring.
I see that you are considering things like tube rolling and new cables. I won't tell you not to do that. Its your choice. I just don't think they will come anywhere near the improvements that a new source will bring.