Maybe try an SM7b if you're going that route? It might be just that much better that you can live with the results.
I have an SM7B... the low end never sounds right to me, for my voice anyway, and it's only okay at dealing with the whistle. It's either too muddy and thick with the low end flat, or too scratchy and weird with the low cut on. The built-in roll off in the 58 combined with an 80hz HPF from my preamp has been much better starting point for me.