Am I crazy to upgrade?

Save your $$ on the Tekton good at first hesr but drastingly missing the detail 

that the B&W  speakers have , and buy much better amps ,Emotiva good for the money but for sure BP not even midfi Highend , buy a coda 5.5 or #8

grest values and quality  rarely advertised but always on back order made in USA.

Love your plan.  Those speakers are special.  I agree with @erik_squires on Marantz.  He recommended Marantz to me and I am very happy.  

Talk to Brandon Wade at Apollo audio systems.  He owns Ulfs and also makes some nice high power SET amps that are perfect to drive them using a preamp out signal from your Marantz. then you put your 2 channel sound system into a second input on the amy (you'll have to ask Brandon to build you an amp with 2 inputs).

Jerry

Great sized room and no spousal acceptance factor and you are good to go.

I would look at where you should be when done. You want equal quality from source to speakers and two channel only stuff is way better than home theater components. Especially the source. When putting together a whole system, lots of research and listening is required to make sure the equipment has the kind of sound you want... like highly detailed with slam, warm, or natural... etc. There are brands that specialize in each. But assuming you are choosing the brands that play to your tastes and are of the best value at the investment level, then I recommend the approximate investment of 35% speaker, 15% streamer, 15% DAC, 15% preamp and `15% amp. Surround processors are not good two channel sources. Then after a year and all is broken in and positioned, start upgrading interconnects and power cords... etc.

One other thought... is there any chance this is a revenge purchase? Big, loud and ugly (to females)? If there is any chance, I would slow down, and go auditioning systems to find the sound you are looking for. I would listen to B&W, Wilson, Sonus Faber and Focal speaker based systems. They are main stream and make some of the finest speakers on the planet.

You absolutely, 100% do not have to upgrade everything else, in fact, it's ignorant to do so until you know how the new speakers sound with your current setup. That being said, I'd bet you'll think it doesn't sound that good and will buy all new stuff anyway.

Sounds like a major life transition, If it's not going to jeopardize your other financial priorities, after doing your due diligence, go for it. Life is short, enjoy yourself. Enjoy in good health.