Seeking more 3d imaging, deeper/wider soundstage

I'd experiment with moving speakers further out from front wall and also at least a few feet from side walls as well.

Try to get sound reflected from primary reflection points on walls based on your main listening position to travel as close to twice the distance as direct sound, in order to get timing of reflected sound correct and also avoid early reflections from being too close to the walls.

That should improve imaging.

Then experiment with positions closer to walls from there but no closer than a couple feet or so to avoid early reflections that smear soundstage and imaging.

Wall treatments might not be needed once the best location for soundstage and imaging is determined. Or if positions closer to walls is needed from there, absorbing wall panels at primary reflection points can help.

Bass levels may lower unfortunately with less proximity to walls for re-inforcement. Optimizing for bass levels and soundstage can be hard to achieve together sometimes. FUrther tweaking of location relative to walls might help, or a sub or subs can be added to add bass extension, if needed.

With those speakers, in a small room like that (I have a room same size practically that I have dealt with but more densely furnished and less bare walls which helps, see my supplemental system photos), bass levels/extension is probably not a problem, so need for subs is unlikely.

A couple feet or so from walls to avoid early reflections may be all that is needed for better results.

Power conditioning may likely help as well but not so much until early reflections are eliminated via at least a couple feet or so to walls. I'd do that first. Its free and easy. Then see what some power conditioning can add.

Don't know about Rotel but the brands Bo identified are certainly NOT all inherently 2-dimensional as indicated. I have heard otherwise.

Magico is a very well made product and very good in this regard based on personal past auditions. Used prices here I have seen recently are coming down as well to the point where Magico used is more realistically competitive on price with other options as well.

Real,

Next thing would be to experiment with a few simple 2'X2' or larger wall panels starting with side wall main reflection points initially, adding rear and maybe others in small increments from there if needed. Need not cost a fortune, look on Amazon for well reviewed products, need not cost much at all if you shop carefully.

Your room is not large, right? If you listen fairly close to speakers, the distance between drivers on the floorstanding Quads could work against you for best imaging and soundstage. Monitors with simple crossover and closely spaced or even coaxial drivers, like KEF for example, will work in your favor. OHM Walsh would be another more radical omni design that could work well. Or other floorstanders again with simple crossover and more closely spaced drivers, like Totem Arro or slightly larger, for example.

Then I woudl also add some basic good quality power conditioning for pre-amp and source gear. THis will stay with you no matter what from there.

I'd look at tube-preamp next after that, if any further need. Cannot go wrong with ARC for that.

Tube amp is the last thing I would go for, unless you are just hell bent on going all tubes from here on out and then let the cards fall anew from there.

I have also found Classe is a very good option for SS gear that is very transparent sounding and images well. THen there is also the good stuff from Krell as well.

Realremo,

Check input impedance of your current amp before going with a tube pre-amp. IF not 30k-50Kohm or higher, it might not be the best match. Not all SS amps handle higher output impedance of tube pre-amps equally well. 50-60K amp input impedance is a pretty safe bet in most cases.

If amp is not a good match, you might end up with tube amp and pre-amp sooner rather than later in any case.