What speaker cable made a major difference in the sound quality of your speakers??

Audio Note SPx silver Litz, one of the few components I doubt I will ever replace.  The retail price is very expensive but I managed to buy mine as a demo from an Audio Note dealer within your budget.

I have to agree with @grannyring . The Duelund 16GA tinned copper is an absolute giant killer. It smashed my $3000 Argento's. 
At $10 a meter, it's a no brainer. 

@rrwolfgram and @wtf - so funny, I’ve been reading that site and a few others like it since @sabai posted about making his own silver cables..

Did you guys use the spaghetti Teflon tubing for insulation? Was it difficult to thread the wire through? Did you use close to the same size tubing or oversized? Thanks in advance.

My main problem is that my speakers need power, so I’ll need something fat, which gets expensive. I’m trying to decide on two possible solutions: either a single run of 10awg then make some jumpers from the same wire, or two runs, one of 12awg to the woofers and one of 14awg to the tweeters and mids. Right now I’m using cat5 diy cables (copper) that have the equivalent of 11awg to the woofers and 13awg to the tweeters and mids. They sound way better than the copper 12awg twisted pair cables they replaced. That makes me think the biwiring solution for the silver cables would sound better, but the copper cat5 could sound better than the copper twisted pair simply because of the larger combined gauge (9awg vs 12awg) instead of the different architecture.

Thoughts..?

Auvio Square Parallel Premium 12 G speaker cable. $0.48/ft (no longer available?)
It's 99.95% O2 free copper, 50% of the strands are silver coated. 
It's not a "jaw dropping" improvement; but a solid one. Wish I could get more.

An 8’ long DIY stack of 3/8" wide .999 silver foil, each foil wrapped in Teflon tape, stacked, and drawn through an earth-grounded shield of tinned copper-braided tubing. About 1.5 lbs. of silver in all, at the commodity price of $750 plus a long afternoon of work.