The Toshiba player will need a digital audio cable (coaxial or optical for regular DVD's; if you want to preserve your two coaxial inputs you could go optical), six analog audio cables (for the HD-DVD discs), and an HDMI cable. If you want to make use of the 990's DVI switching, you'll want an HDMI-to-DVI cable
like this one .
The cable box (which I'm assuming supports HD) will have a coaxial digital output, optical digital output, or both. You'll want to use one of those (it doesn't matter which). What model of cable box do you have? Some have HDMI, some have DVI (MidSouth Time Warner still hands out Pace DC-550's as of last year), and some have component video only. If it has an HDMI or DVI output, you could get an HDMI-to-DVI or DVI-to-DVI cable (which would let you leave the Samsung plasma on a single input all the time and let the 990 automatically switch for you).
The Samsung will need an HDMI-to-DVI cable so you can connect the 990's DVI output to one of the HDMI inputs. You'll also need to run an analog video connection so you can see the 990's menu. If you don't currently plan to have any other video sources in the system, you can just pick up a composite video cable (should be the least expensive option). If you think you'll have other sources (game console, for example), you might go ahead and get a component video cable to go from the 990 to the Samsung (the 990 will transcode any analog video sources - composite, s-video, or component - to the component output, plus you'll still have access to the 990's menu).
The Orb Audio system will need the sub cable you mentioned having earlier, the seven pre-amp cables (from 990 to 7125) that we talked about earlier, and speaker cable from the 7125 to each speaker.