I just hit this site while Googling.
http://www.empiricalaudio.com/frAudio_FAQ's.html

Way more 'data' than I can read or evaluate. But some interesting statements for those that want to debate cables. Lots of charts and graphs. Of course, they wouldn't mind if you bought their products.

Some conclusions:

--inexpensive interconnects having a useful maximum length of about one meter.
Optimized high-end interconnects will have a useful maximum length of about 5 meters.

--it is beneficial to make the speaker
cable length at least 1.5-2.5 times the length of the interconnects.