If you don't have a firewall/router (since most of the cheap firewalls are also routers...) between yourself and the modem you're asking for trouble. I saw a statistic the other day, for broadband users, it takes 20min before they're compromised in some way when they don't use some sort of firewall. =/
Having a 4port firewall/router, is nice anyway, so far as the isp see's you, you're just one person, even though you could have 254 people/connections behind that firewall. I've got around 8 computers on mine at home.
edit: oops...i didn't even answer your question...I just use the onboard one myself. Most pci ethernet cards require the resources of the cpu anyway. Unless you payed $25+ for that ethernet card, i would just use the onboard one (aren't there two on that board? Use the broadcom one [i think that's the brand...] rather then the one with the nvidia firewall built in; it has issues on all the nforce mobos; you can disable the firewall on that one if that is the only one you have). <A HREF="http://www.anandtech.com/mb/showdoc.aspx?i=2465&p=26" target="_new">Article on onboard Ethernet</A>
F@H:
AMD: [64 3000+][2500+][2400+][2000+][1.3][366]
Intel: [X 3.0x3][P4 3.0x2][P4 2.4x5 down][P4 1.4]
"...and i'm not gay" RX8 -Greatest Quote of ALL Time<P ID="edit"><FONT SIZE=-1><EM>Edited by apesoccer on 07/06/05 03:21 PM.</EM></FONT></P>