hosted pbx system for us

hello we are a company with few guys who work from homeoffice. we need a pbx system, where every guys from our team are available on this system. everything must work over voip. we need 100 call numbers and few groups like service, office, grafic, ... who can intall us a pbx system on a webserver? the admin panel must be easy, that we can edit too. if possible, we will start few month an own callcenter with 5 agents. it must be a system, where we can add this to the pbx. please contact us and send us a bid and how long you need for this. if you know an admin panel with german language, it will be better. but not a must.