Unless you guys absolutely foresee a need to do phone support, this isn't a necessary factor. In our case, we had employees take calls with their own numbers (many chose to do this on their own regardless). That isn't necessarily the best option mind you, and it depends on how much control you guys want to exert in tracking calls and all sorts of other factors. Alternatively, we had an Ooma box with multiple lines for taking calls at the office. That isn't necessarily the right setup for you guys or anyone else, but there are certainly different approaches to consider. Many found that having to carry two phones was unnecessary and a pain (in our case).

But unless you absolutely need to do phone support or constant calls, it seems more of an unnecessary cost due to personal wants than to serve a need. All I'm saying is make sure you guys are spending money because you feel it serves a purpose, not because you guys can. Best of luck.