If you were opening a new small office, what networking equipment would you buy to ensure the best quality for VoIP traffic?

Sorry for the non-enterprise question, but this sub seems to have the most expertise in ensuring that VoIP traffic is properly managed.

I'm opening a new small office for a friend (about 10 people) and the staff will need reliable phone service. He's in a Cogent building so he'll use them for an ISP but everything else is on the table.

Thank you in advance for any help.