Sony DVP-NS3100ES DVD Player

I currently own DVP-NS975V unit which has been a good universal player except for its known firmware bugs (i.e. sudden tray-lock and very slow responses) in its earlier production run. Needless to say, my unit had to be serviced and now it is working relatively trouble-free. However, when I learned about new DVP-NS3100ES, I was very eager to upgrade my DVP-NS975V with a supposedly better ES version. When the unit arrived, the first thing I noticed was how well the unit was built. It looks sturdier than my DVP-NS975V... it also has a lot more user controls, especially on its video side. But soon after I played my first DVD movie, my high expectations were shattered. The picture quality is not any better than my old DVP-NS975V unit. Most of all, I hear these annoying popping noises coming from my rear channels through the optical digital audio connection at the start of 5.1 audio playback of any DVD. This is not acceptable for the unit that is two hundreds dollar more. I even tried the same DVDs on my old DVP-NS975V but there were no popping noises. I finally decided to send the unit back for a full refund. I was very disappointed to find another evidence that Sony is lacking in its quality control.