will different lengths affect sound

It's too hard to know the cause when your system is not performing up to your expectations. Why take a chance with something like different lengths of speaker wire?

Of course they will. Point is if you can hear it. And that depends. I doubt that anyone can in case one cable is 6ft and another 8ft. But..maybe someone can. I cannot.

I've always kinda liked this article on speaker cable lengths... http://www.audioholics.com/education/cables/speaker-cable-length-differences-do-they-matter

Funny about 25 yrs ago I was at a dealer playing with different length cables. If I remember correctly he used a 5' and 15' cable. It took a while but I could hear was what sounded like a ever so slight reverberation with the mismatched cable lengths. Some people in the store actually preferred that sound. Anyhow that was 25 years ago when my hearing was better.