My apologies for the late reply on your topic, but you have a few options to consider. One could be moving stand alone sites to a hosted VoIP platform, however the downside to this is that if you lose internet you lose voice. If you choose to go with hardware, like an MCD, you'll also need to get additional hardware such as a SIParator (Ingate). This acts as your MBG and can be configured for of your SIP needs, including codecs, etc. but like with anything else requires licensing. Depending on how many concurrent calls you'll need to support, you'll need to make sure to have the proper dedicated bandwidth. For Example, on a 10Mb connection you could handle up to 80 (80%, industry standard) concurrent calls. This equates to purchase 80 SIP trunks, then dividing them up as Session & Usage accordingly. You can also go with a cloud base platform, like Cloud PBX w/PSTN Calling if you wanted to integrate this with SFB. With this option you move away from purchase desk style phones, but the options are they if say "older" employees want them.
