Before I continue, let me just say this: this information is provided as-is, free of charge, with no guarantees of any kind.
OK, now that that's out of the way, let's try reverse engineering the caps I put in there...
For reference, all part references are specifically for the CT3990. Other models may have different part references, be advised.
C103, C104, C106, C117 and C119 measure between 165~177 nF. So 180nF as a relatively common and cheap to purchase in-bulk value, should work for all these caps.
C131 and C142 according to Yamaha's datasheet for the YMF289B are 12pF caps. They are used for filtering the 33.8688 MHz crystal oscillator; interestingly Creative installed them while using a ceramic resonator as well. (Guess they wanted to err on the side of caution?)
One potential roadblock is the fact that 33.8688 MHz ceramic resonators aren't common, not on Digi-Key at least. I'd imagine 33.88 MHz straight would probably work without any problems. Not sure if a 33.8688 MHz crystal oscillator would work - then again, Yamaha's datasheets indicate that a crystal oscillator of that frequency can be used there, along with the 12pF caps and 3.9K resistor as mentioned earlier. The crystal oscillator would be much better than a resonator in any case, if it works.
So, to summarize so far the parts that need to be added and where... All SMD resistor and capacitors are 0805 size except otherwise mentioned...
U28: Yamaha YMF289B-S
U23: Yamaha YAC516-E (the -E is important, the non-E versions have a different pinout!)
R30: 10 ohm resistor (larger than a 0805; not certain the metric size)
R50: 3.9K SMD chip resistor
R88, R91: 47K SMD chip resistors
C103, C104, C106, C117, C119: 180nF SMD ceramic capacitors
C131, C142: 12pF SMD ceramic capacitors
C86. C116: 1uF electrolytic capacitors
C105: 10uF electrolytic capacitor
C4: 33.8688 MHz ceramic resonator (MAYBE a Crystal Oscillator will work... haven't tested)
U19: TDA1387 DAC
U20: Creative CT1978 CQM chip
C54, C55, C91 capacitors
I've doubtlessly missed something here, so expect this to change as I poke this card further.
Life isn't long enough to re-enable every hidden option in every BIOS on every board... 🙁