Tom:
I feel that the picture quality is noticeably better with the DVP-NS999ES. My 7000 looks a little more edgy and sharp. The 999 has a softer look. In addition, the 999 has many more user adjustments for video. I have not messed with them much yet, but there are tons of adjustments you can make (many more than the 7000).
Per your earlier thread, the 999 is very smooth when changing layers on a dual-layer DVD.
Build quality is good, just like the 7000. The 999 also has multi-channel SACD. The 9000ES is 2-channel only SACD.
Good luck with your choice. Does your S7000 have the switches?