Can AC Outlets really make a difference?

Yes, and 10 gauge dedicated circuits will make a difference also.
Porter ports from Albert Porter of Porterhouse Audio is a good start, if you want a bigger difference get FURUTECH GTX, but they are about 4 times the price. Happy Listening!

Yes the outlet matters. And the outlet box, and cover. Also the wire coming into the outlet box, and how it gets there. One straight continuous run sounds better than wired outlet to outlet with lights and stuff all on the same circuit like most homes.  

Also the power cord, how it gets to the amp or whatever. If it goes across the floor then it will sound better raised up off the floor. Oh gosh this is getting tiresome, hopefully by now you get the point, everything really makes a difference. Why the heck you think my system looks like this? https://systems.audiogon.com/systems/8367

I'll second the above 100% , I'm currently burning in a Furutech GTX NCF (R)  Prior to was the PS Audio Premier and AQ Edison . Each has a different signature but I'm really liking what I'm getting from the Furutech those far. So 10awg dedicated 20amp line and shot for the top.