High level Subwoofer connection

I am in the process of adding a pair of subs to my two channel music system. I plan on using speaker cable from the amplifier speaker output connectors to the high level inputs of the sub (ie, REL recommended).
My questions are:
1. Will the type of speaker cable make any difference (ie., stranded, solid core)?
2. What speaker cable do you recommend using?
In advance, thanks for any thoughts or suggestions you may have.