Sound is too thin. What to upgrade, add or remove?

There are some room treatments available that look nice. Room treatment is a huge step up in a room like that. Even just a couple of panels and maybe two bass traps if possible. At minimum you should research room acoustics. Go to the room simulator at the Rives Audio site. You can put in the dimensions of your room and it'll give you a rough idea where the least amount of room modes will affect your system regarding speaker placement/seating position.

Since you only have digital source, if all else failed, why not try one of the room correction system like the Tact 2.2.

Working with what you've got, I suggest you try these two things....one at a time.
Try toeing-in the speakers a bit at a time from the listening position that you are now using.
If you don't have one, get a laser level from Costo ($18) and that will let you get the two speakers toed exactly the same. IMHO, the "site-picture" of the side of your right speaker really needs to be adjusted IN some, and be sure to make the left, the same.
Secondly, after you find some improvement with that, move your body forward (then back), a bit at a time, from your current listening position. Notice what happens to the soundstage. (Be sure to keep your head at the same height)
Two Bonus trials!
3rdly, from an agreed fixed position (do this one before or after the first two steps)....change the elevation of your head....up and down from your seating position.
And last, walk around the room (slightly bent over so that your head/ears is at the same height as while seated, and notice if there is a difference in the bottom end. (I'm assuming you've got something playing! :-) ...and it has good bass, or use a test-tone CD. You'll probably hear more difference closer to the walls. (the bass should tighten up)
Your seating position also could be at a "null" position in the room.
If you notice a drastic difference on doing this walk-around, you might consider setting up your room layout differently. That might do it if you can get by with the WAF. Otherwise, you'll probably need to (1) EQ the room and lastly do room treatments.
Hope that helps!
Good listening!

Jewel:
You mentioned that your system sounds thin in the last months. Your virtual system is dated 06-04. So comes to mind having a little evolution /time / history of your rig.
Have you made any changes to the system in this time span?
Added new furniture?
How sturdy is that nice credenza? Would you rate it as "ringing" using the knuckle test?
Wood is a very interesting material that depending on construction might change properties with weather i.e. wood is affected with humidity and temperature....How long have you had your system placed on this nice furniture piece?
How about power related factors? It´s hot now and A/C use goes up in the summer right? A little food for thought from "out of the box"
Any luck with different supports under your components?
Your comments please
Luis

ok folks - the sound did improve but not by huge margins. The imaging was certainly more defined, and the overall sound felt less chocked. BTW, I also liked this somewhat more near-field listening position as the speakers were now pulled forward by 2-feet. Unfortunately I ran out of testing and listening time, we had guests over!! I will continue to refine this setup based on all your suggestions. I'll separate the preamp, remove the PS outlets etc. I may also put a layer of padding under the rug.

Sol322, to anwer your questions -- i've had this setup for well over a year; and no, i did not add and/or remove any furniture etc. what i think has been happening is, i've started to go to more live acts in smaller settings lately.

I just wanted say, I'm quite moved by show-of-force - thanks :-)