All the cables mentioned should be an improvement.
When I bought my 25xl's they were very flat and had no highs. The dealer who had just delivered them, went to his car and brought in the cheapest Synergistics speaker cables made, and the difference was BIG.
I have used the Reality Cables with Bel Canto, and now use the very good Teresonic cables, but they are over your budget. Buy used on this site.
Good luck,