go with the S8300, the one dealer might quote you an IP Office because they are not allowed to sell S-series. Both systems are able to do IP phones but the S8300 is the better solution for the amount of phones you have. They can use the same phones too and if you use the cheaper phones (1600 series for the S-series won't work on IP Office) then you might be even cheaper with the S-series system or not much more expensive and you will be happier in the long run. Have the provider that quoted the IP Office give you a quote on the S-8300 solution.
Joe W.
FHandw., ACS
If you can't be good, be good at it!