This is not meant in any way shape or form to undermine Shahrose's comments regarding his own experience with upgraded cables, but there is a polar opposite view on the matter you should at least be aware of. For the most part, the great cable debate is confined to the sound science forum, but in essence, the "anti-cable" faction, if you will, contends that listeners routinely fail to distinguish between the original vs. upgraded cables in blind tests.
There's no doubt that many companies make beautiful, well constructed aftermarket cables out of high end materials, but whether or not you will personally be able to appreciate sonic improvements as a result of buying one is a separate matter entirely. Back when I started reading head-fi, I assumed that cable upgrades were sort of a given in belonging to this community. 1) However, over the past two years, the more I've read on the topic, the less convinced I've become that there is any scientific basis for purchasing expensive after-market cables in so far as attempting to realize audible improvements. They certainly do look pretty, but 2) there is a high probability (some would say, a certainty) that you can reach a more impressive cost/sonic improvement ratio by investing your money elsewhere.
Recommendations for upgraded power cables, on the other hand, simply baffle me. There are a few posters who constantly raise this issue, but I have yet to see any reasonable explanation as to how using three feet of extremely high quality power cable (from wall to amp) is going to make any sonic difference at all when the hundreds of feet of electrical wiring flowing through the rest of my house were wired with whatever stock, cheap cable they used back in the 1920's when it was built.