Dedicated NIC or dedicated port for iSCSI?
Solution 1:
PCI-x/PCI-e bus-speeds are such that unless you're talking 10GbE, dedicating one port on a quad-port NIC is all you really need. The card will have enough bandwidth to handle full-streaming on all ports (whether or not the server it's in can handle that is another story).
Where a dedicated NIC comes in handy is if that NIC can perform as an iSCSI initiator from firmware. This turns the NIC into a dedicated storage adapter, which can be more reliable than a pure software iSCSI stack.