If you haven't seen it already, here's a great article that gets techinical about the science of speaker wire. I use 14 guage from Home Depot myself (about $0.40/ft I think), and it sounds the same to me.

http://www.roger-russell.com/wire/wire.htm

Includes the quote:
"...So what do our fifty hours of testing, scoring and listening to speaker cables amount to? Only that 16-gauge lamp cord and Monster cable are indistinguishable from each other with music..."