Read Oppo's website about the audio advantages of the 980 and 983.
980 is an audio driven machine with like isolated and discrete type analog audio power supply etc... The video is about 92% of the new 983 and 95% of the old 981... However the 981 was built purely for Video quality mostly seen on 50" and bigger displays, however its audio is not as good. video on all 3 is virtually identical on smaller panels from my experience.. But the 980 in my system sound far better than the old 970 and 981... I owned them, and bought a 983 for a trial run, but sent it back deciding to see the new blu ray and better overall unit they will have in the next generation, but the 983 is a little better color and less ghosting and motion blur on the big displays over all previous machines, and the audio is virtually identical to the 980...
For the money my opinion the jump from 160.00 on the 980 to the 983 at 400 is too big.. If they dropped the 980 all together and just replaced it with the 983 for 299.00 then we would have something. The 981 really would not be the best if you are looking for a universal worthy in both audio and video.