24db per channel per the page; even in series that's 48db, which isn't all that much, especially considering at least some high quality dynamics like the SM7 have notoriously low outputs. Not as sure with 58s, 57s and the like, as I never use them.
This isn't even taking in to account impedance matching, and having to use adapters and such.
I'm not saying it won't work. It's just not the ideal tool for the job, and success will partly depend on the level of the source.
EDIT: what I DO like about the Gozinta for this purpose is 4hp. I'd use a nicely spec'd external mic pre and run that line out in to the Gozinta. I wouldn't want to take up more room than that in a rack next to the 301 for level matching alone.