Great setup! Very neat and clean. I love the job you did mounting the widescreen on the wall. I wanted to do the same with my family room t.v. but wouldn't dare try to fish the wires through the wall. With my skill (or lack of) the wires would start off in the family room and come out of the bathroom wall. As far as your speaker placement is concerned, I agree, post 18 is better. Although not ideal as is, I disagree with moving the L/R speakers way over on the side of the bookshelves. With the speakers so far from the screen, you will lose the connection with what's on screen and what comes out of the side channels. An example is when you have a character talking on screen. As he moves off-screen still talking, the sound will follow him off screen and then jump way over there. Also, there are instances where the sound is coming from the half-way point between the center and L or R speaker. With the sides so far from the screen, your soundstage will be adversely affected. Here is a little snippet from an article on speaker placement.
...
the goal of all speaker placement for movie soundtrack playback and multichannel music reproduction -- even stereo --
is a smooth, consistent and unbroken soundstage across the front, coupled with a sense of envelopment in the ambient surround effects. In other words, you're after a sense of location, whether that is suggested by what's on-screen, by the recording venue or even the dry, intimate acoustic of many pop/rock studio recordings.
An Essential Guide to Home Theater Speaker Placement
You should be proud of the job you've done!
Best
Bigdady