You have discovered the importance of impedance matching. One of the things I love about the MIT Magnum MA interconnects is the variable impedance. While I know which will sound best, I always like to try out all the settings to make sure the reality matches the theory and if I ever switch out any components I don't have to buy new cables.
As to driving amps direct with a Wadia, you're grossly oversimplifying both ends of the issue. The Wadia preamp section has never been "shi**y", in fact it's comparable to any decent preamp and much better than low end preamps. But cables or not, the Wadia direct can't touch a high end preamp in the chain. Direct is a great option to have but it's not a high end solution, never has been and never will be.
As to driving amps direct with a Wadia, you're grossly oversimplifying both ends of the issue. The Wadia preamp section has never been "shi**y", in fact it's comparable to any decent preamp and much better than low end preamps. But cables or not, the Wadia direct can't touch a high end preamp in the chain. Direct is a great option to have but it's not a high end solution, never has been and never will be.