Need recommendations on 15ft speaker cables

My advice is to buy a high quality but affordable cable set to use as a benchmark before spending big money.  Erik mentioned Mogami, and Canare is another, both available from World's Best Cables on Amazon, see: Canare 4S11 or Mogami 3082

Once you are accustomed to these, you can try borrowing some Cardas, Audioquest, Nordost, Transparent or other higher priced cables.  It will help you gain perspective on the value of spending more, and we'd love to hear the outcome once you've tried a few.

@ghdprentice thanks for the note. I see transparent reference cables available in market. I was told that they could be custom tunes for past owner's gear.. do you know if that is the case or it should not matter

I am currently using blue jean Rca cables which are all copper 10awg I believe.

I cannot find "Blue Jean Rca cables" listed as a speaker cable on their website. If those cables are in fact an all copper, 10 awg speaker cable, then they should be sufficient for your B&W 805 speakers, assuming a 15-foot length and a competently powered amplifier. What are you trying to change or improve?

I got them from Amazon. I see it is 65 strands totalling 10 awg. 

Ok, then same question, "What are you trying to change or improve?"

There is nothing inherently bad about 10 awg stranded copper speaker cables.  Since you are looking for cables that "provide SQ upgrade," is there something about the sound that you don't like, or that you hope would change with different cables?  Otherwise, you are going to get a bunch of brand name cables recommended by a variety of posters here.  At that point, if you are curious, your options become buying and trying different cables or maybe looking into the lending library at The Cable Company and then you can figure out if something sounds better in your system.  Let us know how it works out.