The PC Connectivity SDK is old and does not work with any Symbian OS based phone.
If your company signs up for the Forum Nokia PRO program (http://pro.forum.nokia.com/), you will get access to the PC Suite API to communicate with phones supporting PC Suite 6.5 or later (assuming the PC app should run on Windows 2000 or Windows XP).
Otherwise, you can use OBEX APIs.
I don't know what "m-Network" is. Do you mean the old m-Router stuff by Intuwave (that used to be part of older Nokia phones and their PC Suite)? If so, then there are no corresponding m-Router bits and pieces on the 6630 or 6680 (the 6600 was the last Symbian OS based phone with m-Router).
Forum Nokia PRO:
Yes, we are thinking to sign up for the Forum Nokia PRO program. But we need to know more about PC Suite API. For example:
Does it work with USB?
Could our PC application to communicate with our phone application and vice versa ?
Does OBEX API work with USB ?
m-Network SDK is a Intuwave´s software. m-Network SDK includes m-router.