Slow and steady, my kind of man. What you are talking about is pretty much what I have been doing off and on since like forever. But especially the last ten years or so. One or two great components a year and after a while.... https://systems.audiogon.com/systems/8367
You are already off to a great start. There really is no one next step or even set of next steps that are all that much better than any other. At least not that we can help you with. If there is something in your system you feel is relatively weaker, you are less happy with it or whatever, that would be the first to go. Other than that though, it is not like what some people think where you have to do speakers to hear anything else, or your amp is the weak link you won't hear anything until you fix that, this is all bunk. You already know it is bunk because you heard the fuse. Obviously your system and ears are good enough to appreciate that, they are good enough to appreciate everything else.
Decware vs Herron is a tough call. I have Herron and love it, definitely a keeper. But it does use an op amp while the ZP3 is pure tubey magic. Hard to go wrong. I find that as more time goes by I am even more drawn to tubes and would lean Decware for that reason alone.
I would for the same reason be looking to upgrade the Mac to Raven. But again if you are happy with your Mac then maybe save that for later. Besides, if you were to do the amp now you would probably go for a Blackhawk or Osprey. But if you were to wait for later after upgrading everything else you might well wind up like me setting your sights on a total end-game Raven Reflection.
I would highly recommend Origin Live. Their arms just work, none of this BS worrying about compliance, cartridge matching, you can forget all that they just work and produce wonderful hard to believe an arm can make so much difference music.
But without knowing what you have that you feel is weak then the one step I can recommend that will be big value and work no matter what is what you already said, Townshend Podiums. And Pods. They also make a Platform, which is basically the damped shelf material similar to Podiums but with Pods underneath. They can make these to any size, just ask John Hannant he will hook you up.
With those you probably want to start with the speakers, then turntable, then amp and other components. I am not big on wall racks for turntables but every situation is different. Whatever rack you use the Townshend will still work and be incredible. The stuff I was already using was very good, and some of it even cost more than Townshend, but Podiums and Pods are so much better it is hard to believe.
Some of this stuff like Townshend you can get right away. Some like Decware you are looking at a couple months build time. Herron I think is about a month.
Another thing I would do, in between the big components, add Synergistic HFT, ECT, PHT. The HFT will be a great improvement to the acoustics of your living space without making it look like a sound room the way acoustic panels do. You might not be able to do the full room treatment because of the layout but the speaker kits are impressive and work on all kinds of different speakers. PHT on a cartridge are almost like a whole cartridge upgrade. Townshend are of course like a whole new turntable!
There is some other even better stuff, PM if you are interested in that I will hook you up.
Couple years from now your system will be so much better it will be hard to comprehend. Exciting times!