M&K is a very solid company which makes very good speakers for home theater applications. You would not go wrong purchasing a system of their products powered by Outlaw Equipment. Another nice thing about their products is that they blend very nicely together. The only problem I could see would be the size of your room. That's a mighty large space to fill. Which model of M&Ks were you looking at for the front L/R channels? The surrounds would work fine with in-walls but I'm wondering about the amount of punch available from the mains.

Also, I would seriously consider twin subwoofers in a room that size. Actually, I believe you would be better off with two subwoofers in any size room!!

Just looking quickly at M&Ks website for pricing, your budget may be in trouble when you start to consider a system of the size you're looking at. I may be a M&K buff, but I'll add that many different speaker companies make speakers of different types that would fit your given set-up. You may also want to consider systems by PSB, Paradigm, Infinity, and more that are beyond my memory at this point. The point being, remember to listen to speakers by these various companies before deciding on installing them. It's not a small amount of money you're investing and you want to be happy with what you end up with. Let your ears decide for you.