Speaker Cable Recommendation to upgrade Tribuataries in Wall UL rated cable

This is probably an issue I should have investigated years ago, instead of constant component searching.  I have always found my system a little thin sounding but have neglected to look at my speaker cable.  I have been using Tibutaries SPB12UL 12 AWG copper cable, as when we built our home we were under the impression we needed in wall wire- which turned out not to be the case.  I wonder if anyone has used this cable?  I think an upgrade might be worthwhile. I am looking for an organic musical sound.  Richer in tonal quality.  Budget 2-3 K for starters.