Remember there's a difference between the max speed the MODEM supports, and your *connection* supports.
For example, we have ADSL; the ADSL modem supports up to 8MB/sec download, but BT doesn't offer that, so we only (!) get 512KB/sec download. A standard modern network card will offer 100MB/sec connection, but it doesn't mean the device you've connected to will necessarily send out data at that rate ... it's just the rate YOUR computer can send/receive data at.