Nice home.....Great with the walkout style basement.......works great for the system you ask about.
If you talked about the K-6, and saw one, you have seen a very good option. Masonry chimney is a must IMO, and yes, it will run on an power vent......I just don't like the additional layer of circuitry for a central heating system. I would leave the Weil McLain just as it is, and find a place for the coal boiler elsewhere. That WM Gold is a very fine boiler, and a dual fuel of any kind will not give you the instant changeover that you can set up your new boiler with. A new setup.....how handy are you?.........or 10 to 15K depending upon your situation. Used or rebuilt equipment can save a lot of cash if you aren't one of those guys who has to have the latest and greatest.
You are at a great time in your journey, keep looking, keep asking, keep thinking...........and look around for local offerings. If possible, get to know a forum member who may be able to keep you from falling into the abyss before it happens. If you want to try out a stoker stove, then by all means, but there are two types of people burning coal: Those who want a Coal Stoker Boiler and those who already have one. You can play all the games to get to that decision, but in the end, you might PASS GO, save a few grand and arrive at ParkPlace without the scars from the 'College of Hard Knocks' and remember a few ole dudes who told you the truth the very first time you asked a question about coal. If you have a thirst for a few years of Classroom with Professor Murphy, he'll be more than gracious to take your money AND later tell you he told you so!
Most of us took that route, anyway, however a few of us who can still walk and talk are offering you some few advice.