Server, Equipment and setup recommendations

We have a client that is looking to replace their phone system and we are trying to gather information and recommendations on how to set this up.

Here is our scenario:
- Main office has about 20 users
- Remote office #1 has about 10 users
- Remote office #2 has 2 users
- They are looking at expanding offices across the U.S.

We are looking at a good setup for using a PRI/T1 that can easily be expanded. So, here are a few questions:
1. What kind of server hardware would be recommended for a 50-100 user setup?
2. What kind of router that supports good bandwidth monitoring, QOS, and VPN would be recommended?
3. What kind of bandwidth would we need over the internet? They currently have a single T1 at each office.