AVM Competition DAC2 upgrade

Hi,
I have old 1998y. AVM Competition DAC2 with dual PCM63 dac chip. I'd like to make upgrade receiver and digital filter chip or for me better make NOS DAC. Receiver chip is Yamaha YM3623B and digital filter DF1700P.
1.OPTION: is to replace Yamaha with DIR9001 and DF1700 with SM5842 or PMD100.
Signalling pins are compatible but not all others.
2. OPTION and for me better to make NOS. In that case I don't need receiver and filter chip,just USB->I2S board like JLSOUND which I have.
PCM63 can directly accept I2S signal from Jlsound.

I/V can be also upgraded. There are 6 opamps 5534D (JRC) which can be replaced.
I asked AVM for schematic but unfortunately they not support DIY.

Any suggestion
 

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Already did option 2. Cut PCB input on PCM63. Adjusted jumpers on JLSound board for PCM and connected directly to the PCM. Just put 22ohm resistors between. Immediately started to work. Sound is absolutely different. Very very good, maybe little to detailed. But this is first step. JLSound board is getting power from USB, galvanically unisolated. This will be next step. After that is coming I/V stage.
 
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