Film caps!
The stock electrolytics are quite good. But film caps can have even lower effective series resistance. But they are physically huge at 220 uF and 600v. You can use a choke in place of a resistor between the caps (clc instead of crc) to lower ripple enough that smaller (lower capacitance)caps make sense.
Having done this, I can say it sounds better to me than stock, but not by a great deal. It's subtle, and not the first place I'd spend my fancy cap money.
