Assuming that you have an 867-988-xxxx, it appears that DIDWW is in turn buying the DID from Iristel, as they are the only CLEC in your rate center. »www.telcodata.us/search- ··· state=NT
Their physical interface to Bell is not analog POTS, but PRIs or other TDM technology, depending on capacity (number of concurrent calls). It's most likely in leased space inside a Bell tandem office.
However, the IP handoff to you might be in a larger city, with Iristel or DIDWW backhauling TDM to a central location. If you point the DID directly at your SIP device (requires forwarding the SIP port, proper NAT mapping, and dynamic DNS unless you have a static IP), you can receive calls without a SIP provider and can easily see where the audio packets are coming from.
If you are really that concerned about latency but want the feature set of a SIP provider, find one that does not proxy the media; it could be anywhere.
However, IMHO latency is relatively unimportant -- even an extra 100 milliseconds is hardly noticeable. Choose your provider based on quality, reliability, support, features and of course price. If you are otherwise happy with VoIP.ms, by all means stay with them.