Chinolee112,
The most important piece of information is with the following analogy:
If I had to pull a caravan and I fit it to the back of my car, I would have no trouble pulling it, right. The caravan was designed to be pulled by a car.
Now, imagine that instead of a car, I am using a large SUV or Truck. Pulling it will be sweet as pie.
The same goes for the system you chose. What was it designed for and what are the resources that it has? The IPX was designed to handle over 80,000 ports. What was the Cisco they recommended designed for? Will it handle to call processing easily, swiftly and effectively? Cisco will not hide this from you. Ask them for the Busy Call Hour etc.
Have you talked to your local NEC rep and told him your predicament? Tell him to get this document for you: (you cannot get it, it requires and authorized NEC vendor to get it)
There is a document there that compares NEC to Cisco.
The document lists over 350 points of interest!!!
You will see that there are a few versions of Call Manager that go from 100 ports to 30,000 ports.
Here is a sample comparison:
CallManager/MCS-7815I 100 to 300
CallManager/MCS-7825H1/I1 - 1,000 to 4,000 devices per cluster
CallManager/MCS-7835H1/I1 - 2,500 to 10,000 devices per cluster
CallManager/MCS-7845H1/I1 - 7,500 to 30,000 devices per cluster.
Which one did they propose? Was it the car or the semi-trailer? If you want to go from one to the other, is it a fork lift upgrade? Etc. There are more than 350 points of interest to consider!
Does NEC have competitive dollars to help you. Ask your NEC rep. Many companies put away money for strategic accounts. In my books, you would be a strategic account. Try.
Also look at our web site. We have an article written up on voip. It was written a while ago. We are working on a follow up:
see article number 103.
I am not recommending one way or another. Just make sure you get all the help you need. Also, it would only be fair to call a local Avaya Rep too. It will help you see all angles before you make the decision.