New setup

The NAD is a good choice for the Focal because the Focal tend to be bright and somewhat lean/thin in the midrange.  The NAD will warm things up, fuller midrange, and take the edge of the highs.

I don't have experience with a room that large, but I think I have read that you may need a lot of power and speaker to fill that large room.  It's not to say that the Focal Aria bookshelf will sound bad.  It may not sound as loud/big as you might expect.  I would ask around about large rooms like yours.

Heh, asking about speakers will generate about a dozen different opinions, and everyone thinks they are right, lol.

In my own listening, I think the Monitor Audio Silver series is the best choice at your budget.  I tend to avoid metal dome tweeters because they are bright/metallic sounding due to the metal breakup.  The Monitor Silver is a ceramic coated metal and it's the best one I know of.  I would say it is second only to B&W D3 series (which is synthetic diamond tweeter).  The Monitor Audio will have extremely good resolution, especially in the midrange.  Good body and fullness (better than Focal in my opinion).  Crutchfield might still have a pair of "open box" Monitor Audio Silver 10 for $2k.  They also have several Silver 8 models.  Or you can opt for the new Silver series (such as a 300 or 500).  If you get a Model 10 or 500, you might not even need a subwoofer initially.

NAD would still be a good choice as the Silver series is just a tad bright.  (In my opinion, the ribbon tweeters of the Gold/Platinum are way to saturated/bright).

  Inappropriate gear for the venue

Heavyweight speakers and amps might overpower a small room, but I don’t necessarily consider that a bad thing. Overkill is generally good, whether it be wattage, horsepower, pizza, or Nutella. What is inappropriate, however, is a low-powered system with low-sensitivity speakers in a large room. And you can exacerbate that problem by not including sufficient subwoofage. Most often, speakers with a sensitivity rating of 86 dB @ 1 meter will not work well in a 5,000 cubic foot room, regardless of the size of the amplifier. In a larger room, you may have to step up from a receiver to separates, and move to speakers that handle more power and have higher sensitivity. And if your 300-watt 10” sub makes rude flatulent noises during loud passages, it isn’t necessarily the sub’s fault. If you have under-spec’ed a subwoofer for a room, you can compensate somewhat by placing it in a corner where it will couple better and have more output, but in some cases may sound boomy in a corner. Consider buying multiple subs. Not only will the output be cleaner because each driver and amp is being driven less hard for a given system SPL, but you can place them strategically in the room to smooth out the room modes. If two are placed laterally on opposite midwalls, they can minimize the null to improve bass in the center of the room where most people place their seats.