well, I'm a TARA Labs Master Gen 2 user. I have their interconnect between CDP & pre + their speaker cables. From whatever I know about the TARA Labs Ref interconnect & speaker cable, it is exactly how you wrote it: polite on the top-end.
From one TARA Labs website I visted sometime back here is what I found for the Reference speaker cables:-
RSC Reference Generation 2
Very revealing yet smooth. Offers overall increased performance over Prime cables. Greater transparency. Slightly forgiving in high frequency response.
the very last comment seems to jive w/ what you are hearing!
upgrading to Master Gen 2 or to the Decade should solve your issue.
I also believe that the newer generation of TARA cables - RSC Air1 - for both interconnect & speaker are better than the prev Decade model.
I personally like TARA Labs so my reco is to stay w/ them. FWIW. IMHO.