Count me in your thread as one more satisfied Acoustech 5.1 setup owner. I bought my set about 5 years ago - yeah, I was always an early adopter... Their price back then was about the same as one pays nowadays. They were the best bang for the buck back then for around one grand and they still are... It is the combination of price, looks and sound, really...
BTW, congrats to your huge HT room. It is a luxury really to have such a big dedicated space - consider yourself lucky!
Now, the reason behind me posting is to give you some suggestions regarding your speaker placement (not like you called for any, plus it is really just one person's opinion so take it with a grain of salt). There is nothing wrong with your placement, really, but you might want to try some the followings:
The center could be moved closer to the TV, for example could sit on an installed shelf. I will try and post some pics later if you want me to regarding how I solved that issue. Besides better localization of sound and picture that actually would free up some space on top of your furniture.
You could also move your front towers a forward a couple of inches more and install some sound absorbing panels right behind all three speakers. Heck, you could paint the whole front wall (or all the walls room!) darker. The final result could look more theater-like, besides the acoustic benefits. Some wire management could also be done. (Now, if you would elevate those speakers too they probably would have to be tilted forward a little which would be probably harder than with the center.)
The sub could also sit on a hard platform to further enhance response, although your corner location helps with that greatly already. (Besides acoustic room enhancements I am also a believer of speaker paltforms or spikes.)
Lastly, the rear speakers could be elevated a feet or so higher to create direct line of sight between their cones and the listeners' ears. They could then also benefit probably from slight tilting.
OK, I have to admit it is probably the ENVY speaking from me - these would be the things I would try to further enhance the experience IF I would have a space like that...
(Now I should really shut up before I start writing about 6500K lights behind plasmas, bass shakers under the couch, etc, etc...
At the same time looks like you have all the basics covered - I am sure you are really enjoying your setup!
And let me just repeat; thanks for the thread! You are really helping some people here. There is not much info out there on these Acoustechs.
Best of luck;