The manufacturer will of course tell you that for best results you should use their product throughout your system. Heaven forbid that another brand gets in between theirs and prevent you from reaching audio nirvana.
Some really high end components include custom speaker cables, power cords, etc. You should probably throw those away and get a full loom of something else.
As you may guess, I'm a bit of a cable skeptic. Not in the sense that they are all the same, I can hear audible differences between cables.
However, I would rather pick up good used cables at a heavily discounted price and piece together a system with high quality cables of different brands than to pay list price for a full loom of cables throughout my system.
If you have the funds to do so, and it matters to you, I don't think it's a bad thing and certainly will look better than the mess of cables I have behind my system.