Try the website I linked, you can see by the wire table you're fine now; Roger Russel's a former director of McIntosh. Now while 12g certainly won't hurt, it's just not necessary and it won't be audibly different. The fluance blog thing isn't very helpful as far as determining the math involved,
here's an AH article on the subject. You simply need sufficient gauge for the job in terms of impedance and length.
That said, many of us do just use good copper 12g cables to account for different speakers and lengths with a single stock to draw from, I do; I buy it in 300ft reels, like this
https://www.monoprice.com/product?c_id=102&cp_id=10239&cs_id=1023903&p_id=2790