I have owned the Terminator Plus along with the Gaia DDC for almost two years. I haven't heard the DCS Scarlatti, but have heard the Rossini on a number of occasions. The Rossini was in a more expensive system (not in mine) so I don't have an apples-to-applies comparison, but I think the Terminator Plus acquits itself very well compared to the DCS DAC.
The Rossini is a bit more detailed, but the T+ sounds a bit smoother (more analog) to my ears, but these differences could be attributed to other aspects of the system that the DCS was used in. However, this same system playing LPs did not exhibit the edginess I heard on vocals from the DCS DAC. This system is a very high-end system (I'd estimate > $300K not including the analog front-end) and is very revealing.
Both these DACs are very nice. I tend to like a lot of detail, and for some content the added edginess of the DCS is a plus for me, particularly for things like guitar and percussion. But I prefer the sound from the Denafrips (and my friend's analog front end) for vocals (particularly female vocals).
But without comparing them in the same system with the same content, it's a little hard to come to specific conclusions.