i see - if your network port is connected to a router which can only 100Mbit, than changing manually the speed to 1 Gbit will have no effect - except that communication stops between both devices .... you need either a direct cable between 1 Gbit ethernet ports or a gigabit switch between them.
be aware of the dumping strategy of too many suppliers and don't buy switches which are too cheap .... often their backplane cannot handle the traffic appropriately - stay with trademarks a cisco, 3com, netgear (t name a few) - i had bad experience with D-Link and LinkSys lately ...
8 ports for about 100 USD/EUR should be the range of good quality devices ... same goes for additional network cards btw, use intel, broadcom, 3Com even if they cost a few bucks more ...
the PCI-based switch you are referring to probably leaves the work to the computer - so i cannot recommend such a device ...
christian
and remember: only a CRAY can run an endless loop in just three seconds.