I work in the A/V industry, just remember the average profit margin on eqoipment is 30-40%. The average profit margin on cables, highend or lowend is 75-80%.

The only expensive cable you will really hear/see a difference in are: S-video, Video(the yellow one) and Long speaker runs.

Absoulute Truth.  Use optic when you can for audio (From DVD/Sat/etc.) to receiver, then good video/audio RCA type cables for what you can't run optical.  Shielded is good.

Do not skimp on the speaker wires, though, especially if you are over 1k watts.  That does make a difference, especially when running 30 ft. to the surrounds.  The Monster "Flat" cable is pretty good stuff for surrounds (hides nicely along edge of floor).

Try to find a buddy that works at a pro-audio shop (hmmm. bigscrun? [:D]), they usually get stuff at about cost +10%, you would not believe the markups on all audio, car audio is the worse.  (Cost on $699 MSRP Rockford Deck: $197).  

Don't try to get everything through a favor (they work on commission), just cables and the smaller stuff.  If you buy the rest of your equipment from him at 'standard-ish' pricing, he will appreciate the commission and be more willing to help you out on the quality wiring for a good price.

I don't want to recommend more $$$, but I would also recommend Filtered Monster Power strip (Another item you might want a 'friend' for pricing, they are around $150+).  Got rid of interference lines in my screen, have no idea where they were coming from, but it cleared them right up.