Keep in mind, going the mod route saves you the added expense and anxiety of a digital cable and a second power cord. (Anxiety because you have to worry about whether you have made the best choices. Some of us like the angst, though.)
My impression is that most of the mods are strictly parts upgrades. This raises a fundamental question in my mind: What is the relative importance of parts quality vs. circuit design? Of course they both matter, but what I am asking is, can you take the basic Sony (or other brand) circuitry and get near state-of-the-art performance merely by upgrading the parts? Or is a different circuit design needed? If I had any engineering background, I might have an informed opinion on this question.