cable length

I agree with Elizabeth, get the very best you can afford. I would also suggest keep the speaker cables as short as you can get by with. Power cords, again they are by the foot cost, so that must be concidered. If you agree with that power cords can improve your system, than the longest you can afford to maximize the benifit.

Jadem6 is right. Shortest possible speaker cables and longest possible power cables (but there is a point of dimmenshing returns beyond about 6 feet).

Just a question on the same topic. I wonder if it is harder to sell cables under 8 feet? This might be a factor when considering purchases.

Be careful, there is nothing worse than a cable not long enough to reach, some speakers like Thiels need at least 8 feet between them and depending on circumstances maybe 9 to 10 feet. So if you ever change speaks... Also resale is not as good IMHO.

I disagree with the statement "get the very best you can afford." This implies that more money will buy better sound, which may or may not be true. It is very possible to put together a rather mediocore sounding system with very expensive components. I say get the one that sounds the best in your system. Of course, this means you must audition various cables in your system, which is a lot more effort than simply buying the most expensive thing you can afford at the moment.