Long Run From Computer to Stereo

I have Echo Layla 24/96 soundcard with analog outs. The analog outs are 1/4" outputs that are going to require a rather long run over to my stereo. That length will be approximately 35-40 feet to get it situated properly into my tube preamp. Obviously i will need to get the RCA adaptors for the preamp end. But can anyone recommend such a length of decent quality cable for such a set up? I don't expect it to be the best quality but just something decent. I don't even no where to begin looking for such an animal in 1/4" runs of that length.
Right now i am running guitar cables(which sound decent) to my studio monitors but they are only 20' long and i don't know of any cords longer then that in music stores?
Thanks!