Is there really such a big difference between NIC's? I've bought two 
network cards from MS Tech for 4€ per card. They implement the Realtek 
8139 chipset. One of them is connected to my adsl modem the other one to 
a 100MBit Switch. Would I notice any difference if I would use some more 
expensiv network cards? Or is this something you have to believe in?

Greets
Daniel