I would like to make a correction from my post above.
C6 & and C7 are critical so you should use high end cap such as Mundorf or Jatnzen silver or equivalent.
3. Cap C6 & C7 may not be critical. They along with inductor L2 form a notch filter at around 2.5KHz and most of the time, there is no current through them. R4 is actuall more critical (see below) so again, use some basic audiophile grade cap such as Clarity.
C6 & and C7 are critical so you should use high end cap such as Mundorf or Jatnzen silver or equivalent.