Your old DAC is a much cheaper product using consumer level outputss (RCA), which have per definition a much lower output level (consumer level vs studio level).
The claims on the webpage about this product are interesting
"[...]The V90-DAC has a balance of measurements: distortion, noise, linearity, bandwidth, and phase, which in their totality are not significantly bettered by any product at any price.
If you hunt around, you may find the occasional DAC that claims to have slightly better performance than the V90-DAC in one area or another, but in totality will not exceed it. There are plenty of competitors shouting about their new, wonderful version of the emperor’s new clothes, but they offer little or nothing in real performance to back up their claims. Just lots of talk about subjective this or that, but all of it is just a matter of opinion. [...]"
X10SRi-F, Win7 Prof, Nuendo 8.3, UFX+, Octamic XTC, ADI-2 Pro FS BE/DAC, RayDAT, ARC USB