You can tell by my name (NBX) that a have an agenda when it comes to VoIP products. Regardless, I'm not impressed with the way your potential vendor is selling you a solution. You need to learn about what you are buying before you spend $1K a person on a system. Pick up the yellow pages if you need to and call 5 vendors and get them all to examine your needs. The Avaya and Cisco gear is quite different and their willingness to swap you from one to another is not a great sign. I doubt the Cisco gear is cost effective for such a small office and The Avya IP Office is not typically sold with IP phones. (they are often sold with 6400 series phones not the 46xx IP phones -- look at your quote)
In addition, you should understand what their service plan covers AND what data infrastructure improvements are planned, if any. VoIP depends on the data network so these should be part of your fact finding.
IN NYC I know Teledynamics, they sell 3Com's NBX, Avaya and Toshiba.
http://www.tele-dynamics.com/ Do your homework and find the right solution for you.