The stock DL-III is very good indeed. The Cullen Stage IV upgrade improves the stock unit by eliminating (or at least reducing to inaudibility) the slightly shrill harshness in the upper regions (many DACs in this price-range suffer from this), and by improving the bass region (slightly tighter more controlled). The Cullen upgrade to me was definitely discernable, but in a more subtle way than I was hoping for (not a night and day difference). For me, the taming of the slight harshness in upper frequencies was worth the upgrade price. Some(those with the well-trained ears or more acute hearing than me) claim that the stage IV upgrade greatly improves the soundstage by opening it up. I dont hear great improvements in the soundstage via the modded unit over the stock unit. I do however, prefer the overall presentation provided by the Cullen upgrade, and I think it would be very difficult to find a better sounding DAC at this price point....IMO - for what it's worth.
PS audio digital link 3 or similiar Dac
I am in need of a new Dac and this one is on my radar. As there seems to be a plethora of these available, I would appreciate some comments on the sound quality of these units. I am looking to get something that has a slight warmth and not clinical and hyper detailed. Other suggestions would be appreciated. How about Cambridge Dacmagic. These don't seem to come up very often.