Mike, the general rule is that digital audio (coax or optical) will carry the best audio signal vs. the red & white rca audio cables (analog) on the back of your VCR, DVD player, and cable box.
Also, component video will provide the best video signal unless you have DVI or HDMI on your cable box or DVD player. S-Video & composite should be left for VCRs and camcorders... maybe video game consoles.
Stay away from retail stores with Monster Cable. You can pick up perfectly reasonable video cable at Wal-Mart for just a few bucks compared to Monster. The quality will be enough that you will be plenty happy and still have cash left over for a few DVD rentals and some 6-packs.
Cash is good - but a credit card with a $500.00 limit will save you a ton of cash if you are willing to start doing some online shopping. I've saved AT LEAST $5,000.00 vs. new/retail pricing by purchasing online new & used gear.
Speaker cable should be measured by the actual wire gauge (thickness) of the cable. 16, 14, 12 gauge etc. Not sure what your is, but going with a 14 gauge or better wire is strongly recommended by many.
S-Video is not anywhere NEAR HDTVish. 480i is 480 lines of resolutions of video. This can be carried on a composite connection, and it looks better on your S-Video connection... HDTV is typically 1080i... That 1080 lines of resolution. S-Video never is better than 480i - so it is never even close to 1080i HDTV.