Seeking more 3d imaging, deeper/wider soundstage

Hello! I have a similar sized, small room, and I can assure you that some affordable acoustic panels would be my first concern towards improving soundstage and imaging. Without them, you will never know how good things can sound in there. The foam you mentioned is cheap, but not very attractive. I would suggest some cloth covered, 24" x 48" panels such as the ones from Acousticmac for around $40 each, or some DIY ones for much less is you have some free time. The next thing I would do would be to pull your speakers out into the room a bit more...They appear to be too close to the rear walls, and you should not need them that close seeing that you have a powered sub to enhance the bass. You might also try getting your sub out of the left corner and moving it somewhere between your speakers.
Once you try those affordable "tweaks", then consider upgrading your amp or pre-amp. The RB-1080 is a strong amp, but not well known for it's soundstage or imaging abilities. Keep an eye open for a JOB 225 amp on the used market if you can stretch your budget around 15-20%....Great amp! Enjoy!

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.

All the above is great advice. Start with maximizing speaker placement. Looking at your system pics, I am not surprised by the lack of soundstage depth. The sub may need more placement tweaking too. After maximizing placement, only then would I start down the path of room treatments - which you very well could still need.

Here is a good place to start: http://www.cardas.com/room_setup_main.php

Be patient and do everything in a step wise process ALWAYS listening to your preferred reference track between each move. Good luck - I know you will find the soundstage depth and width you want!

What great responses...kudos to everyone for not immediately jumping on the "buy this new amp!" bandwagon. I completely agree...you have a fantastic grouping of components, you should be very proud. Before I'd spend a penny on any electronics replacements, I'd do exactly what everyone recommends and experiment with getting those Quads out into the room, maybe 2-3 feet from all walls if possible. You really do have nice components, nice speakers (have always liked those Quads), I have high expectations that you are probably no more than some placement tweaking and/or wall treatments away from audio heaven.