Then keep the SM7 for gods sake. The mics you mentioned will not outperform it. I would say the NT1A is a big step down, and the KSM27 a sidestep - at best. Don't get fooled by the common belief that a condenser is automatically better than a dynamic.
The SM7 has been used with excellent...
For the Queen sound, use a Brian May Red special through a wall of VOX Amps. Cheap? No! Maybe you could get something close enough by using the Vox Tonelab.
But really, the killer thing about the guitars in "We will rock you" is all in the attitude of his playing.
The reason I mentioned the KSM44 was that is has switchable polar patterns, meaning you could go omni if you had a group of a capella singers at the same time etc. You would have a highquality LDC with different polar patterns, and (if you keep the SM7) a highquality dynamic. For being "only"...
I think the problem lies in the fact that your converter doesn't convert the Hz difference, only the Volts. Which would make some things not work correctly.
Don't know if it can be harmful to the actual equipment though.
I would suggest you keep the SM7, forget the NT1A and save for the KSM44. Then you would have 2 of the most versatile mics out there IMO.
I have 17 mics and would never consider sell my SM7.
I can't for my life understand what the argue is about. Use the best bass available and put on new strings. Any other decision would be stupid. If the bass player won't spend the bucks, knock him out and replace him.
You still need a DI box. However, if you're preamp has a 1/4" instrument in, which may be what you meant (sometimes called "Hi-Z input"), you can just plug your axe there and won't need a DI box. The instrument in means the preamp got DI capabilities up it's sleeve.