Where to put budget

Trying to decide where to put my money for next improvement.  Deciding between surround back speakers, better subs, or room treatments. 

Specs
marantz 8802a on dedicated 15 amp line
(2) Lexicon rx-7 amplifiers on dedicated 20 amp lines 
oppo bdp 103
revel ultima studio 2 (left/right)
revel ultima voice 2(center)
revel ultima gem 2 (side surrounds)
(4) revel c783 atmos in ceiling 
(2) Svs pb 1000 subs
panasonic tc-p65vt60

room is roughly 16 x 17 but not a perfect square as front sits under a bay window.  System may be overkill for this room but five year plan is to make this room 20x28 so don't want to underbuy

what i am solving for:  I'd really like to get stand mounted gems for rear speakers to get the full 7.1 sound system set up/ full immersion.   I do have a decent set of revel 585 in wall speakersthat I could use for surrounds however I noticed a huge improvement and sound field when I switched from low end side surrounds to the revel gems. I think having gems in the back will me a good starting point from which to do anything else as I don't plan on upgrading them ( thinking of them as foundational). 

The base in the room is not how I want it.  I do have two subs and I have played with Odyssey I have moved them around but it still seems boomy.   Not sure if different subs or room treatments will improve this. 

Imaging is another area id like to improve for two channel but I'm a little constrained on how far out I can move the speakers.  Right now they are about 1.5 feet from back wall and 1 from side/back wall(it's an angle). Granted I don't have dedicated two channel going to these speakers but the equipment upstream is mo slouch and should give at least some depth. If anyone has recordings they'd recommend that have fantastic depth please advise.  My current budget is ~5k keeping in mind I don't want to do too much to the existing room as I plan to remodel it at some point.