I'm looking into replacing our comcast phones here at work with an actual VoIP solution that would give us API access to stuff like texting and placing calls.
I'm looking at renting a small PBX server from vps.powerpbx.org (have under 10 employees, so that should be fine) and then getting a SIP Trunk from Twilio.com (since we are web developers & want to have it for its handy APIs too).
Is there something else I'd need, or is that all of the pieces we'd need to make it work?
I think you have all the basic pieces in place. But it comes with a few gaps.
Building features on telephony for PBX specific features can be a bigger ask than having the bare infrastructure of making calls and doing text. I work for a cloud phone provider and have learnt that making the call is the easiest part of getting things work. Getting it to do IVR menus, innovative integrations and making it cohesive, scalable and high reliability is the challenge. Also having the ability to use it across devices makes it more appealing as it grows.
I shall recommend checking it out with some low cost Cloud providers instead of building it yourself. Unless its a skill and expertise that you want to gain to extend your business.