Before you condemn the receiver (or even the speaker wires) try connecting a regular CD player to the receiver and listen to some decent quality albums.
Computer audio and MP3 files are likely to be inferior to a good CD. Though I own a number of MP3 players I gladly spend weekends at flea markets going through the CD albums that iPod users are practically giving away.
he is exactly right, dont listen to anything other than a CD when testing audio equipment.
Also, your speaker wires are OKAY, but i would definatly recommend an upgrade. No reason to have those kind of speakers and kill yourself between them.
the Yamaha HTR-5930 is a decent receiver for the money, or it was. I dont mean to bash your gear, not my intention.
Depending on how high of a listening level you are playing these at your sound quality will become lower.
In short, i would say you made a great buy with those speakers. Put some CDs in and listen away and see if it corrects the issue. You could then try to get some good quality speaker cable and see if it makes a diff (it should), if its worth it to you buy some more.
If its the receiver thats creating the noise problem, dont feel too bad, Just another reason to get some new gear
This is the best place around to get cables.http://www.knukonceptz.com/home-theater-speaker-cable.cfm