When I used to manage a computer store I ordered 6' Cat5 cables for around 75 cents a piece.
Do you need Cat5e or 6? 6 won't give you any more speed if you don't have a gigabit NIC and router/switch. And all existing lines from the switch to NIC would have to be Cat6 for it to do anything. Also, what do you need 1000mps for?