Hi! I saw your post in my "$2500 Complete System" thread
Your situation is a challenge. Shipping to Saudi Arabia is very expensive. It makes much more sense to buy as much locally as possible.
The TX-NR818 is a fantastic receiver. It might be a little bit of overkill for your budget and room size. But it is never a "bad" choice. You are correct that for other zones, it will only send stereo analogue audio. But this is the same for almost all receivers. Very few will send a digital audio signal to other zones. Especially more than one other zone. And any that do tend to be very expensive.
If you want to send audio to multiple rooms in your house, I'm afraid it still makes more sense to simply have a system in each room. Especially if you want to stream the music wirelessly. It makes more sense to have a little network connected box in each room, and then use self-powered speakers connected to that box.
For speakers, since they are big and heavy, it makes more sense to buy those locally. Do you have access to the entire Klipsch family of products? I'm not a huge fan of Klipsch brand speakers themselves, but Jamo and Energy brands are also part of the larger Klipsch company. You mentioned Jamo is available.
I'd have to suggest that you simply audition what is available to you locally. Both Jamo and Energy make some great speakers. So of those brands are available to you, I'd recommend you have a listen to those.
The biggest challenge is going to be the subwoofer. I know that HSU will ship almost anywhere, but the shipping charges can be very expensive. Still, given how good HSU subwoofers are for the money, it might still be worth it. Out of the brands you mentioned, nothing really comes close to the Internet direct subwoofer brands.
So, as long as the Onkyo 818 fits your budget, it's an excellent choice. For speakers, I'd suggest buying locally, with Jamo and Energy as top choices. And for the sub, it might be worth the high shipping cost to go with HSU. Also look into SVS. I'm not sure what their shipping policy is to Saudi Arabia.
Hope that helps!