Hey Aziz,
The surrounds are not crucial. Use whatever you have, and it'll be fine. You can always change your mind later if you wish. but I doubt you will.
Electronics don't matter much, but I would recommend getting a Denon, Marantz, Yamaha, or Pioneer if you can. Onkyo historically has some longevity issues, particularly with their HDMI boards. Pay for the features you want, but don't spend extra for higher watts. Most listening is done at less than a watt anyway. If the published sensitivity of your mains can be trusted, you won't need much power to drive them.
The weak link in your combo is the subwoofer. There's no way a 10" sub is going to pressurize an almost 8000 cubic foot space. Where do you live?
Sent from my LG-VS980 using Forum Fiend OSP v1.3.3.