I would order two HDMI cables online and another that has a converter that makes DVI turn into HDMI. Then you need only one optical cable. The HDMI can be routed through the Receiver from the DVD player and the Cable box (you need the HDMI-DVI adapter to connect the cable box to the receiver. Next connect the optical cable to the cable box and route it to the Onkyo Receiver. HDMI can carry both audio and video on the same cable, so you only need to make one connection between the DVD player and the receiver. The cable box, since it only has a DVI output, you will be needing the optical cable because DVI interface only does HD-Video, not audio. Last run the HDMI output from the reciever to the television.
Good Luck,