Inexpensive speaker cables

Belden zip cord of appropriate diameter

after that, get something you can return and have a friend substitute it in (or not and tell you they did) in a double-blind test

you will be unlikely to hear a difference and if you do it will be different but not better

that looks pretty good - breaking corrosion at the connections when removing/reinserting cables is often responsible for some of the difference in sound people think is due to a new or different cable

a fairly large dia. for speaker cables, yes - but be sure the conductor is large; some cheapo cables have very fat plastic insulation and thin wires!!

most cables are "Oxygen-free copper" except maybe the cheap imports and... if they say Oxygen-free copper how do you know it really is

Belden is a quality name for all wiring

also, there are some liquids containing conductive polymers that you can use to coat the connectors; I have a tiny bottles form many years ago, and I think it might even be called Tweek ;]

that will help reduce corrosion at the connection

don't worry about that - the value is dubious at best

just get some decent cheap cables in there; do some room treatments

worry about spendy cables after you have spent your first stack of $10,000 bills on top notch speakers