First if you are really into gaming you want to get that sofa off the back wall a little bit. Even if you can pull it forward a couple of feet it will give some room for a rear soundstage to develop even if using only 5.1 surrounds placed just behind and to the sides of your seating. I game a lot and you don’t want to mistaken the direction something is coming at you from if it’s behind you. I would shoot for at least 1 meter which based on your picture is doable. This will also help your front speakers especially bookshelf and in/on wall better reach your seating as it will move your listen position closer. It will also likely make your front speakers sound better by delaying the reflection off the back wall which will likely interfere with the direct sound coming from the front if the sofa is up against the wall.
That said if you are focused on mostly movies and games I would prioritize the following based on your personal preference.
1. Get a good subwoofer that goes down to 20 Hz. For movies and gaming this will really pay off.
2. Get a good center speaker for movie dialogue intelligibility.
3. Get very diffuse surround speakers because of the limited distance behind your seating and because of how close the left wall is.
4. Get timbre matched speakers all around so that 360 degree pans in games sound seamless.
Based on that I would recommend 2xM22 mains, 1xM22 or 1xM2 or 1xVP100 center (preference on the matching M22 and then M2 because they sound so similar and are both less expensive than the VP100), 2xQS8s (stick with 5.1 for now and if you can’t pull the sofa off the back wall I wouldn’t even waste the money on 7.1). The sub is a tougher choice. I haven’t heard the EP350 but I’m inclined to say you should go below the EP500 for a room of that volume. Not sure if there are any other sub makers in a similar or lower price range in Canada but if so you might also look into them. The sub is one speaker that doesn’t need to be timbre matched to the others so a different manufacturer isn’t a problem.
Even if you don’t have room for bookshelf speakers sitting on the floor I would consider putting up shelves and using regular bookshelf speakers instead of on or in wall. IMO you will get a little better performance out of them and have more flexibility if you ever want to move them somewhere else or even sell them.
I agree on the refurbished Onkyo or also a Denon receiver though other brands will do fine if you can find a bargain for something with the features you want.
If you plan on this system being with you for a while I wouldn’t skimp on any of your speaker selections. IMO it’s better to build a system piece by piece and get what you want rather than trying to get everything at once if it means downgrading a speaker.
Cheers,
Dean
