I also have a startos. I am using a CAL Alpha DAC with 1963 GE Long Plate Tubes. I love my DAC, it has let me know there is more to CD's than you've previously heard. As far as SACD, there is not a whole lot of titles out there. The SACD format is amazing, I've heard it on a Sony 9000 DVD/SACD player. It sounds great for SACD, but I feel your current CD selection will benefit from a DAC. Wait a year or two till they have a combo SACD/DVDA player. There are a lot of reasonable DAC's out there, but a Tube DAC will let you change the sound.
Regards
Regards