Of course you can.
Soundreef only deals with royalties, we're not publishers. We manage your royalties, but we don't publish or distribute your music.
This way, you're free to choose the publisher you prefer, whether they're registered with Soundreef or not.
The only important thing is that you always correctly indicate what shares your publisher owns when you register your tracks. If something changes, you need to notify us immediately by contacting our customer service team through the help widget in your account or through the contact form on the website.