Wow... links to the Monoprice.

1st) The company that Chinese distributing, counterfeiting, ripoff, stole that from is Mantle Mount (what Mantle Mount gets for building their stuff in China). And their 4 strut mount is only rated to 125lbs. The Monoprice one only has 2 struts.
Does it really surprise you they would lie? This is the same company that got caught a few years ago, selling copper clad aluminum Cat5 cable with counterfeit UL labels.
But what do I know...

By the way, Fins is right. It doesn't matter if the lights are out, it is going to look like crap. But the customer will probably think it looks fantastic. People will such low standards are like that. They only care how cheap they get it for and how quickly it is done.
So get your check but if I were you, I would not use that Monoprice mount for such a heavy setup. Probably regret it...

Real brick fireplace = no problem. Just make sure you get your anchors into the brick and not the mortar. I like using A10 Alligators with 3/8" lags:
[Link: toggler.com]