Good Tweak for Perpetual Tech P-3A

I am looking for some good tweak I can do for my Perpetual tech P-3A DAC. I already heard about changing the OP-amp for Burr brown OPA-627AP but I was wondering if they are drop in replacement for the opa134 stock op-amp, and which one of the opa627 I need? (AP,AU,BP,AM). Any other good tweak suggestion?
The ringing P-Tech chassis are a problem that is very easy to solve.
Cromolin VC ("CVC") Damping Material kits, designed by Don Moses (aka: Mr. Wadia).
Simple 5 minute tweak that gives an improvement top to bottom.