General notes-
C301, 307, 308 are raw power supply filtering.
For CD audio (sourced at U103 PCM decoder), start at U201 (DAC), come out stereo to U202 filter (caps C205,C206 significant here),through U203 amp/filter, through U504 audio gate, into U505 (caps c617,c618). Out U505 (through caps c613,c614 -- also, c616 sets frequency response) to U506, out U506 (caps c604,c610) to AV output connector. Same signal also fed to U507 amp/filter (through caps c670, c671), then output (via c678, c679) to headphone connector. U507 also uses caps c675 and c676 to set its filter operation.
For game audio (sourced by U901), come out stereo through caps c878 and c879 into U506, continue as above.
For ADCPM audio (sourced by U502), come out mono through cap c652 to passive filter (uses c623), to one-half of U503 amp , out U503 (cap 653) through passive filter (uses c621) to other-half of U503, into U504 audio gate (both channels), continue as above.
C526 is the VCC cap for U515, the 512K ROM.
C323 is regulated power filtering.
Somebody should start tracking this stuff in one of the "sticky" posts, maybe as a table of what cap does what.
Good luck.
Charlie