Hearty congrats on your progress. I have both a Sterling Virtuoso and a Besson New Standard. I'd heartily recommend that you keep both. I agree that the Sterling has a richer sound overall, but the Besson has a nice focus, quirks aside, that continues to draw me in. PLUS, if you're going to be pursuing a music major you can keep one horn at the school and one at home... save the trouble and risk of hauling your only horn around for home and school practice.
I'm in a similar boat. Just retired from my prior day job and I'm headed to college in the spring to pursue a music major that I put on a back burner 45 years ago. I plan to take the Sterling to school and leave the Besson at home. My immediate challenge is prepping for the audition... quite a task for a previous "hobbyist" euphonium player!
Best luck,
Pat
Sterling Virtuoso Euphonium, Denis Wick 4AL