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

Tried many cables over the years ... some cheap ... some expensive
Finally found the right fit

Clear Day  Double Shotgun

Been with them for a few years and will not entertain any other

My speaker cables cost more than your price range and were purchased new but honestly they make absolutely no difference at all to the sound. Extremely solid and the highest quality robust connection is all I have observed from using industrial/military/aircraft grade style connections.

If your system is "singing" at its best, then may I suggest (no I'll say urgently suggest) you try Townsend Isolda DCT Speaker Cables. www.townsendaudio.com from here in the UK. They are the best speaker cables I've ever used (and I have tried lots over the years) and when used with Townsend Seismic Podium Speaker Stands you will get a "jaw dropping difference"
The sound is dynamic, has dimension, with clean non boomy bass and is wonderfully relaxed.
With the dollar/pound exchange rate in your favour why not give them (both) a try. You will not be disappointed. BTW, I have no connection with Townsend -- well only my Avalon Eidolon Diamonds.

I've experimented with cables over the years, and have come to the same conclusion that the founder of Monster Cable finally fessed up to: expensive cables are a gimmick conjured up by marketers who figured out that audiophiles will pay a lot of money - even an insane amount of money - for wire (those with wife problems need look no farther than what can be wasted on speaker wire). IMHO, the discussion around interconnects are akin to a theological cult. 

Unless they are are really cheap wire bought at a hardware store, it's not gonna amount to a hill of beans. The Meineke muffler slogan applies here: "I'm not gonna pay a lot for this speaker (interconnect, etc) cable!"

If it was Crazy Eddie's idea of insane prices, that would be a different story!!!