Please forgive me mate, but you did ask for a sanity check so here it is. You've gone bonkers.
I blame the internet. And certain posters here don't help either.
You're in a very small room in an English terraced house, about to splash a lot of cash in a misguided last gasp of pre-fatherhood life.
You seem perhaps not to have onboarded the hard but wonderful new facts of dad life.
In every possible way you're planning to waste money (Dutch & Dutch, you're kidding, no? Wonderful stuff at crippling prices) on a system that's way, way bigger and more expensive than you need or can use. I mean, you are now considering two subs with Hypex 400 Watt RMS / 1200 Watt peak Class D amps... that go down to 20hz at whatever bananas SPLs people with big houses can actually use? Your neighbours will hate you, yes. Your child will be traumatised also.
And yeah, you are totally overvaluing cardioid. It's hip round here, because this place loves clever new gear. Clever and new don't mean much if they don't fit real life.
Take it easy and go slow. I would seriously suggest you don't spend all your dough all at once, that way lies sadness and disappointment.
Get a budget and stick to it. £5K is plenty. Keep the other £5K in a tax-free wrapper or maybe buy the kid some shoes or biscuits instead.
Get some quality bookshelf-size speakers and wall-mount them, as others have suggested. Get a miniDSP to EQ your speakers for your room, since your partner not unreasonably does not want fugly room treatment, or fine, let the NAD + Dirac do the fiddly stuff.
Get an SVS micro3000 sub if you must, for the (let's be real) brief moments when there a) isn't a tiny child sleeping in the house, and/or stopping you from sleeping because that's your life for the forseeable and b) the neighbours are out. The great advantage of the SVS is you can adjust the level separately and remotely. Whereas you can't on the Buchardts, and you're going to be killing the sub volume a lot. Lastly, get some good headphones.
Happy Christmas! Sorry if I come off all negative here, and best of luck to you.