While we don't recommend PBX hardware, we've installed and configured quite a few of them. The Vicidial Group is expert at this, and Gardo is also quite good. I'd be careful with anyone else unless they have a good reputation and have experience with the actual equipment you're using.
That being said PoundTeam has been providing all these services since Vicidial version 2.0.4. We provide support for tiny items (carriers, phone configuration, quick code mods) and large projects (full custom application coding in agi/php/perl/AJAX/MySQL as well as Multi-Server Vicidial Cluster Buildouts) and everything in between. We also have consultation levels available to allow one of our techs to "help out when needed" instead of doing all the work for you (this allows your team to come up to speed without having to pull out their hair while getting there!).