I am using the new Burson dual op-amp in my modified. It replaces a DEXA dual op-amp which replaced an LM4562 which replaced the stock NE5532. The Burson Supreme op-amps offers better tonal balance and tonal detail, the DEXA being a little more open and extended in the bass. The Burson also seems more rhythmic. Both discrete opamps easily outclass monolithic opamps.
The Onkyo has numerous mods to it including rectifiers,. power supply caps, signal path caps and Takman resistors. Though the original is good, the amp is now in an entirely different class. In fact, I now prefer it to my vacuum tube separates.