As a matter of fact, almost nobody here will tell you to buy the best cable you can possibly afford. What you should do is buy the least expensive cable of good quality. In the audio world, spending more money doesn't necessarily mean you'll get a product that sounds better. This is expecially true with cables.

That being said, a few places that we often recommend for cables are Radio Shack (no joke), Parts Express, and Blue Jeans Cable.