Room size & choosing speakers

I used to own the 802Ds, 803Ds, and 805Ds and I will say a
10x12 room is definitely too small unless you spend some
effort into room treatments. I personally would start with
the 805Ds and go from there adding a sub as required. BTW, I
used to be in 25x20 room and now have a 10x11 room. I am
currently using some SF Auditor Monitors at lower listening
levels and it works great for me.

10x12 do not get floor standers. I'd go with the 805. You may not even need the subwoofer.

another consideration is this... how long are you committed to having the system in that room? That is, are you permanently confined to that room? Will there be a move to a different place soon? I had a friend who invested in a system for a small room --- he painstakingly matched the system to that room. Then two years later he moved had a room w/ 3 times the volume and his system was now ill equipped for that room. he sold the system losing half his money and started again. Perhaps if you overload that small room for a time and use room treatments (a cheap option) --- then, when you move, you have a system that need not be replaced.

Of course, that may be your permanent room (or semi-permanent). Still, get a full bodied system that will play most anywhere and use some room treatments. That is the cheapest and most flexible route to take... or, at least, so it seems.

In all probability if your goal is to recreate the magic you heard at the dealer you will fail by a significant margin. The room and its interaction with the loudspeaker is the single most important aspect of getting great sound. Most dealers have spent more than $100k exclusive of equipment just to get the room right. As a non-professional user you don't have to go to that extreme, but a basic understanding of room acoustics and the use of products and techniques to address common problems is very important.

The magic of hearing well reproduced music is not primarily a function of equipment. Instead it is more about correctly setting up and matching equipment. For less than half the cost of the system you heard at the dealer there are knowledgeable audiophiles who could assemble and set up an equally magical system. B&W and McIntosh are both very good companies, but there are other brands that offer better value. This plus the knowledge of how to properly setup equipment, particularly loudspeakers, can save a consumer money.

I have no opinion about the B&W loudspeakers you mention. Tboooe has extensive experience with that brand and I believe he has given you some good advice.

Great sounding but overkill...
The 805's should be the place to start with no sub-that can always come later. The C50 is great. The 302 should sound exactly the same but is only 300 watts. That is more than enough power. Honestly, 40 watts with those speakers in a room that size will suffice. Yes, I do understand since I'm using a mac at home.