Why not have everyone call in from their own machine? This way, it normalizes the communication bandwidth between everyone, no one feels like it's harder to be heard. A big failing of many remote teams I've seen is when they try to "strap on" a remote team. But if you can minimize the feeling of "real office vs virtual office" it works a lot better.

generally a good idea but we need some kind of conference system, if there is a meeting at office #1 with e.g. four people, to connect the one or another colleague form office #2.