Dedicated line: 10 gauge solid core or 8 gauge stranded

Hi everyone,

I'm having a dedicated line installed for my system. I read recommendations to run a 10 gauge wire, but I thought, why not 8 gauge? It's my understanding that there are no receptacles that would accept the thickness of a 8 gauge wire, so my question is: is it best to run a 8 gauge wire all the way to the receptacle and then bring it down to 10 gauge with a junction box to connect to the receptacle, or, just run a 10 gauge wire from panel to receptacle??
Also, the 10 gauge wire the electrician showed me was solid (just 1 thick wire), while the 8 gauge wire was stranded. Does that make a difference for sound? Which gauge would you go with?? 

Thanks!

Pierre