I currently have shotgunned 4TC and have had stotgunned 8TC/4TC (8TC for the lows, 4TC for the highs). The 8TC/4TC was overblown in the bass and overall not as refined and neutral as the 4TC. Above all, I would not use 8TC for the mids and highs, as you are intending. As others have said, if the speakers are made to be bi-wired, go with 4TC/4TC, either shotgunned or two discrete cables. I love this setup. In my system, I do not find it wanting in any regard.
