Just looking at the equipment and setup quickly, it is a big space to fill 'properly'.
Volume-wise you can probably get there but it probably won't sound too pleasant. A lot of hard surfaces and also the wall next to the right hand speaker won't be doing anything good acoustically and becasue you don't have the symmetry with the left speaker (which is just out in open space) it's unlikely to be able to create a solid image and indeed much lower mid-range and low end. The highs could be a bit shrill due to the aforementioned hard surfaces and indeed the equipment. The XTZ's are good amps but being Class D they are neutral, some would say a little clinical and unexciting. I have no direct experience of them but I have had experience with Ice Power amps and Temple Audio mono's both of which do have similarities.
The Topping pre is also known to be a little clinical, in my experience to get the best from Class D amplifiers a tube preamp can really bring them to life or indeed an active preamp which is on the warmer side of neutral.
I'm having trouble finding specs or anything on your Onkyo A-6130S, all I can seem to find is a network streamer? I do like the sound of most Onkyo amps I've heard though, usually sound a lot more powerful than they actually are.
As others have suggested the room is probably robbing you of a lot of elements of the music here. The mid-range and lower end is slightly missing and the low end doesn't have much impact I'll bet. The highs are probably there but by the time you get to any sort of volume when the drivers start to deliver some low end grunt and bass, the highs have become too much.
My suggestions would be to play with placements and room interaction first, you might do better swapping your hifi for where your TV is or even better than that (I suspect) putting your hifi in front of the window 90 degrees to the left of where your TV is. Then hanging some big curtains directly behind it. That would use the parallel walls to act as a symetrical and more predictable listening space where in my experience, things should sound a lot better.
You could also try putting a few more soft furnishings around, like a duvet or pillows in the corners or some curtains along the sliding door but it's still a massive space to fill properly.
If none of that is working it may be your preamp is just a bit sterile and lacking with your XTZ's, I know it measures very well but sometimes components just do not have the synergy.
Don't give up hope, I've had systems sounding horrible at first but after careful room tweaking/speaker placement as well as changing some (not all) components, things have always turned out well. I don't give up until it does!
System 1: - Amp - Musical Paradise MP-701 mk2 - Neurochrome 686
- Source: Audio Technica LP-5 - Custom 6V6 stage - Novafidelity X30 - Soekris 1421 (LPSU) - Custom TDA1541 C3G DAC -
- Speakers: Martin Logan Prodigy's - Subs: - REL T3's -
System 2 - Amp: Musical Paradise MP 303/Custom 300B SET - Custom 6SL7 Pre -
- Source: Pioneer N-30K - SONCOZ SGD1 -
- Speakers: Loth X BS1's - Sub: REL T3 -