Looks like an excellent top-lopectomy!
I made a built in for a large 33" CRT tv, but planned on a big screen for the width. The top shelf could be lowered to match the different HxW ratio.
That all worked out well, but the cabinet depth to fi the CRT went deep into a closet behind. For with a big screen there is a 2' wasted space I'd love to recover.
Your top cabinet looks like i'd look well as anĀ armoire with a new base.