I finally managed to add IC sockets for a number of op-amps in my RS-B965. Along with some DIP8-to-SIL8 adapters I bought from Cimarron Technology, Inc. it is now possible to experiment with different op-amps to see how the sound is affected.
The only disappointment would be the two headphone op-amps on the headphone board, which is in a tight space against the left edge of the deck. It doesn't look like there is room to allow the SIL8 op-amps to be replaced with DIP8 packages.
Now, it's time to go on an op-amp shopping spree...