There are many good phone systems out on the market which can do just about anything until you start to get involved with T1's or PRI's. You want a phone system that will grow as your business grows and can offer such enhancements as voicemail,e-mail and even VOIP phones. I worked a lot with the Comdial product. Check them out at
Also keep in mind that the bigger dealers of a specific product can give customers better deals on equipment. A 24 month warranty on all parts is always a plus. If you need more details, just shoot me and e-mail.
GOOD LUCK!