Is it possible to get a VOIP phone, and use it for dialling out over voip, and also to plug the eircom phone line into the same phone for receiving calls on the existing eircom number?
I think the [broken link removed] and others can do this but I believe it may be tricky to configure. Its also possible to set it up so that you can dial your own Eircom number say from the office and use it as a gateway to make say an international call over VOIP at low rates.
There is a service called which supplies these with their own customisation which looks like it would be simpler to set up but I am not sure if they ship outside the US (and I have no experience of using them so I can't recommend them or otherwise but it looks interesting).
The link below is a Skype phone which will alow you to do both. However it can only be used with Skype and not voip buster, voip cheap, or SIP providers.