This may be a silly question but...

It's funny you should bring that subject up but a friend and I tried some Vampire Wire 10 gauge hook up wire and we both canned our expensive speaker wire. This is the Continious Cast Copper wire that comes in two colors black and red. Michael Percy and a couple other places had it in stock but I should have purchased more of this. Vampire Wire still stocks the 18 gauge wire but the 10 gauge is pretty good wire and may breath new life in your system. At least it embarrased the expensive silver wire I was using. It may not do this in all systems. And the cost is under $3.00 a foot on last check.

I've actually used the standard household electrical wire you're asking about. This was several system iterations back but the upstream gear was still decent: an LP12 Valhalla with SME IIIs and Shure V15-VMR was the source. Had no money for better cables so used 12 ga house wire. Sound was OK in the bass, gritty in the highs and hard in the mids. I moved with some relief to something else which had better highs but less bass, then upgraded again when I could.

Some even cheaper wire which appears very similar is Magnet wire. Surplus Sales of Nebraska has it for about 60 cents a foot.