Wow, you're going to get yourself into a lot of trouble fast.
So, you've made a good start buying flyable speakers with the essential flying hardware.
Me personally, I'm using KV2 Audio. My gear is rigged with fly points. This summer I'm buying some additional hardware so I can fly them in case a promoter wants to do that.
When I've worked shows where the PA was flown, it was done via chain and motors. Considering this is NOT a fixed installation, that's why motors and chains are used. I however am not a certified rigger and I won't fly hardware myself.
I've seen flying done with steel cable for fixed installs, but it's smaller boxes and fewer per individual hang.
First, in your situation: why isn't a speaker on a pole sufficient? Is this mobile?
Second: You'd want to have a chain rated for as heavy as you can get. Most of the stuff in hardware stores is intended ot secure something, like a bike. It's not intended to secure things to a moviing vehicle, such as a wrestling ring to a trailer or a load of heavy logs.
This really all depends on what you want and how you want it done. If you hang via 1 point, your speaker can swing and twist. Not good. 2 points and you minimize twist, but can still swing. Use 3 points and now you can steer up/down as well as reduce swing. You want to of course get these over people's heads so they can't grab or hang off them. Trust me, no matter how stupid you think people are, and how much you prepare for any possible thing they can do, there's some idiot out there who wants to out-stupid the rest. Do your due dilligence, it's best you can do. Short of an electronic cage to electrocute anyone who tries to touch the speaker(and that's gotta be an insurance and fire marshal issue), there's only so much you can do.
If I were you and you wanted to fly the rig, I'd spend a little money if you have ot and talk to a local large sound company and/or lighting company. You might have to pay them for time, some won't charge you. Like if you were to talk to me about it, I'd probably not charge you for it. But, and I know my phone number is in my signature here, before you call me, let me remind you again that I am not a rigger and I personally DO NOT FLY my speakers because am not a certified and qualified rigger. I am NOT certified, and I am NOT qualified. As this is a tremendous safety issue(a drop CAN kill several people at once), it's not something I want to take on myself until I can pass some sort of rigging program. Based on the show I am working on, I am motivated to acquire those skills though. My wife can help me with the math, she's a freakin' math wizard.
If you're doing a permanent install, most civil engineers have sufficent skills to help with loading and things like that. Your contractor can help you here as well. MAKE SURE THEY've DONE THIS BEFORE!!!