The top shelf of the media center is at about 27" - 30", if my guesswork is correct.
The speakers are better served if you move then to the front edge.
In my experience, hollows below the speaker, as in a media center, can start adding to the overall sound.
I have a entertainment center and tried "cubby hole" placement, see the link below.
http://www.hifivision.com/speakers/60593-kef-r300-demo-unit-4.html#post680717
The speakers misbehaved so much that I started doubting whether I had purchased the right speakers.
The idea of stands is to simulate the floating of speakers in air. I learned this after I got stands.
Gel pads on the top plate, spikes on the bottom plate and a mass loaded column.
All of these contribute towards tighter precise bass, less muddiness, etc.
In my case, they really help in moving them as far away as permissible from walls and providing adequate separation between them.
In your current setup, it seems like you may not have the opportunity to do any room treatment.
In such cases, speaker placement and support from AVR/IA in the form of tone/channel controls are your options.
Keep a lookout for front ported speakers; they will be more manageable as compared to rear ported ones.
There is hard wall corner on the left and glass back on the right. These surface may pose some challenges.
Cheers,
Raghu