Where to purchase cables?

I agree with @lak who posted above about Veritas Cables. I started with one set of their Magnus XLR cables and love it so much that I just ordered a set of their higher end Argentum R silver RCA cables. I'm also considering power cables and maybe a few others from them. Just very impressed with their sound so far, as well as their customer service.

I can also recommend other small brands like Audio Art and Triode Wire Labs, they both offer great value. 

Audiogon and USAudiomart both have lots of other nice options. I enjoy Black Cat Cables, Cerious, Decware, Audience, Waveform Fidelity, and DH Labs among others. 

DHLabs, Zavfino, Morrow Audio, Anti-Cables....all make excellent cables at affordable prices, and at different levels of cost and quality. Great places to start

Power cords: whatever came with your system, because anything else won't matter one single bit. 

Speaker wire: any well made 12AWG OFC. Monoprice and Blue Jean Cables are cheap and effective. A coat hanger would literally sound just as good as any expensive snake oil brand but may be tougher to work with. :)

+1 for Morrow Audio