I am using the t brackets. My jbl's were basically mounted flat also. The jbl's I had before only had 2 3" mids with a tweeter. I believe that Audyssey set mine up at around 80. I have my fronts set to 60 and everything is fine. As to the A2-300 for a computer system, I hope that it is your my system. The A2-300 is a lot of sub for the money. I have it close to my sitting position, but I can feel it move my pant legs.