I am reviewing a few different proposals at the moment for my company to do something similar. The most attractive proposal at the moment is for us to rent the service for HK$14,221 per month.
This service includes an Alcatel system with 100 phones (incl 1 operator), IDAP X 2 (with 46 voice channels), efax service x 100 (fax to email), voice mail 4 ports (200 hours), simultaneous ring for 5 users, 4 port analog port for voice gateway (which I am led to believe is the magic ingredient which allows us to connect offices together and have free calls between offices).
This is through PCCW and the service/plan is called "One Communication".
Another quote I have is about HK$120,000 to buy an NEC SV8100 system. But the company has only quoted me 30 handsets and I need about 100. This is from a company called Tact Technology. TACT Homepage. I dont vouch for them in any way and not sure how my staff found this company, I just happen to have one of their proposals in front of me now and I am having a read through it.