Volume Control

Here is one more question for my backyard speakers installation.

I want to install volume control; source will be an Adcom 535, through approx. 50 feet of gauge 14 cable. It does not need to be weather proof, and I want something that does not degrade sound quality; any suggestions? I've been looking into this:

http://www.outdoorspeakerdepot.com/vrautrvoco.html

Thanks!!!!

Unless you are planning on having it cranked up all the time.....and assuming that their stats are correct you should be ok with that.