If you’re sticking with USB, a newer DAC may be better depending on its USB implementation and interior clock. Ideally, what you would want to do to compare apples to apples, is get a really good streamer like an Aurender N20, then plug its SPDIF and USB into your DAC simultaneously, and listen to both. Then do the same with DAC #2, and see if you hear any differences. USB uses the DAC’s clock, SPDIF the streamer’s clock. A lot of variables. It would be a shame to throw away a great DAC because it sounded bad with one input, and you were never able to hear it through its other inputs. So, with USB only, theres a good chance you could get something like a Pontus, prefer it to your Bel Canto, and get rid of the Bel Canto, when it fact it was overall the better DAC…and you’d never know it. And then a lot of people swear by cable quality, especially for SPDIF. So testing conditions become important.
Lastly, you really need to live with a couple DACs for a long time to start to appreciate any differences. Especially if one is new. Break in is real with DACs. And in the end, differences can be very subtle. After only a few days, you may come to one conclusion. Then if you wait weeks or even months, you may come to a different conclusion. Try to have fun with it!