Hi Steve,
I think the 414s are a good all around performer. They don't do the bad things a lot of affordable condensers do and they do some things really, really well. They are great on guitar cabs and really shine when it comes to capturing rich details in the lower frequencies.
I have a 609 and a 906, if you have the sm57 then buying either of those mics will feel like you just got another mic.
If you get a 414 you'll start moving towards a what you hear is what you get experience with the preamp gear you own. The reason I zero'd in on this particular mic is that it has great smooth yet bold character and avoids the various and common mid frequency problems you can learn about with almost all the other mics in that price range. It's not a stepping stone mic, it is a pro grade utility mic.
The next step up in mic budget is hard to justify until you are trying to chase down a perfect match for a singer or some particular acoustic instrument... and if that's the case you will, by definition, end up wanting a few mics to cover those special needs.
As you imply... that's a different type of shopping.
best regards,
mike