Wow, Zxa5 for a 40x40 room? I'd say that's way overkill. 1600 square feet is a small space as far as I'm concerned. Zx5/Zxa5 is a whole lotta speaker and can handle a lot bigger space. I just heard the new EV Live-X ELX15P and they sound really good. They would probably be more than enough for 1600 sq ft and 300 people. Of course adding subs always makes your sound fuller and richer.
Honestly, a pair of good 12" speakers with subs would work well for 1600 sq ft too. I use either EV Sx100+ or EV Sx300 with EV Sb122 subs. It sounds great. They're all plastic, but they sound great and they're nearly indestructable. Whatever you decide, EV makes very good speakers that will last for many years-I call that a good investment. The Sx300 also comes in a powered version. The best thing to do is call NLFX and talk to Ben, he really knows his stuff.
Honestly, a pair of good 12" speakers with subs would work well for 1600 sq ft too. I use either EV Sx100+ or EV Sx300 with EV Sb122 subs. It sounds great. They're all plastic, but they sound great and they're nearly indestructable. Whatever you decide, EV makes very good speakers that will last for many years-I call that a good investment. The Sx300 also comes in a powered version. The best thing to do is call NLFX and talk to Ben, he really knows his stuff.