Do I need 10 gauge power cord if I have 10 gauge from panel?

I have had excellent results using the power cords the manufacturer selected and included in the box with a component.

Paul McGowan of PS Audio used to sell his own line of power cables until he used a full loom of top-line Audioquest cords. The performance improved to the point that PS now endorses AQ cables and no longer makes their own. @kingharold  You may be having excellent results with your stock cables but that doesn’t mean you might not hear even better results with aftermarket cords. I had aftermarket’s on all of my gear and then I had a Paul Mc type experience with my Shunyata Research NR cables. No going back once I heard my system with them. 
 

one caveat…never use power cables or any other type of aftermarket wires on your system that you can’t afford. 

I think I have a pretty nice system. Yesterday our internet was out and left with nothing else to do I sat down to listen to my system with my vinyl rigs (what do you streaming-only folks do if your internet goes down?). The first side or two sounded good but then after about an hour I found myself feeling uncomfortable. Something about the sound was annoying me but I could not for the life of me figure out what. I tried listening to different records including some that are known to be good. No change. I turned it off. 

My point, if there is one, is that everything matters. Sometimes you can't figure out what the problem is. It might be you (me). 

8th-note

Watt meter is nice but it doesn't in my view accomplish everything you want.

Not sure it measures the extremely high speed changes in Power fluctuations needed for Music.  
Isn't the benefit of larger gauge wires throughout the electrical food chain to avoid any unnecessary impedance when power demands occur?? As tiny and subtle as they may be for all those gentle nuances in sonic transmissions.

@fsonicsmith1 Bad AC perhaps?  The one thing that nothing but an AC Regenerator or top notch power conditioner can help with. This is especially important to consider if you live in a high density population area or are near a commercial zone “dirty” AC  can be a very real problem.