OK, I see a few things right off the bat that are not good for decent sound. Since you say there is nothing you can do about the general arrangement, some treatment measures would be worth trying, and here they are. If I am off base on these, somebody set me straight, please.
1. The speakers are sitting roughly on a plane with the front of the cabinetry. If you look at pictures of really nice audio setups, you will see that very often they bring the speakers way out in front of the amplifiers and other equipment. This not only limits reflected and diffracted sounds coming off of the equipment, but also by locating the speakers closer to your listening position, allows for a bit more of a "near-field" listening position. A more near field position will increase the ratio of direct sound vs reflected sound. So, I would try bringing them forward at least as far as where you have that subwoofer, or even a bit farther. Of course, you will want to reset your speaker distances in the receiver menu.
2. Again, if you look at pics of high end setups on hard wood floors, they will always have a rug or carpet placed in front of the speakers. That hard wood floor is likely causing all kinds of reflected sounds at the listening position. Perhaps try a nice looking carpet from the front of the speakers and extending 8 feet or so.
3. There is such disparity between the space around the left speaker vs the space around the right speaker. The right one has all that open space beside it, while the left one is right up against an untreated wall. IMO, you have all kinds of reflections coming off that left speaker and wall. What you could try is to affix some decorative sound-absorbing treatment panels on that left wall, just in front of the new speaker location after you move them forward.
I don't know how much these modifications will make, but I think they should help some.
FAMILY ROOM SYSTEM--Legacy Signature II tower speakers, PSB Image 5T tower speakers, Denon AVR-X5200W, Krell FPB 400cx, Oppo UDP-203 UHD Blu-ray Player, RCA HD-DVD player, Samsung HL67A 750A TV
MASTER BEDROOM--Dynaudio Audience 82 tower speakers, Outlaw LFM-1 sub, Yamaha RX-V1800 receiver, Sherbourn 5/1500A 5-channel amp, Oppo BDP-83 Universal Disc Player, Panasonic 60-ST60 plasma TV.