Hi 69Busboy and welcome to the forum.
I think you may be getting a few things confused here, so I'll try to straighten those out first.
The ART MPSTV3 and the Scarlett 2i2 are different things. The ART is a standalone, tube-driven microphone preamp. The 2i2 is an audio interface (AI) which includes mic preamps. In context they are both mic preamps, but the 2i2 connects to your computer while the ART doesn't (and would need an AI to be recorded into your DAW).
I think perhaps what you're referring to is the fact that the SM7b is renowned for having a fairly low output, even for a dynamic mic, and so needs some sort of gain boost to be properly usable. Some mic preamps on AI can't generate enough gain to keep a clean signal so it is advised to use an in-line preamp, powered by the phantom power coming from the AI to give clean gain to the microphone. The most used/quoted ones are the Cloudlifter and the Triton FETHead.
The ART to which you refer will most probably have enough gain for the SM7b, but it is a tube preamp and designed to deliberately colour the sound of the microphone, whereas the in-line preamps are designed purely to add clean gain.
69Busboy wrote:Preamplifiers make a significant difference,
This is true, although it's not always a good difference.
So, I guess the first question is what are you currently using as an audio interface?
