Ground side to OPAMP capacitor replacement?

[Destroyer OS.]

I have an old CD player, ADCOM GCD-575, not bad sounding with the 1541a DAC in it... Anyways been working on it, threw in some .47uf NX HI-Q's I had for output caps at the RCA's (50uf bypassed was way too much, and .01 was a little light).

Anyways at the OPAMP that the ground eventually returns to there are two what appear to be 50v 33uf capacitors. I bypassed them with some Wondercaps I got for free from another friendly board member, and while they sounded smooth, too smooth, as they where sloppy at 20%, I just could not take it, metal lost it's sound.

Anyways what I am wondering now is how crucial the amount of capacitance is here, and the voltage. I imagine the voltage actually never ever exceeds 4v as it is in the circuit that supplies the (pot adjustable) output signal. Further more I wonder how important the capacitance is... I have a bunch of BG N's but the most capacitance I could get is about 24uf with a lot of work, I could also bypass with 4.7uf's, just use 10uf's (or combo to 24uf), or I have some 50uf FC's.... Any which way the stock ones are harsh, but the Wondercaps I had at 20% where way too sloppy for anything but Depeche Mode.

Anyone got some ideas?