Wyred 4 Sound STP Se preamp tweaks and upgrades ?

My STP Se pre has gone over the 500 hours break-in period and sounds truly fantastic.
I am trying to find out about any tweaks or upgrade mods that may be available to this unit even sound better, if possible.
The other most important thing I must admit is that this Wyred 4 Sound STP Se preamp is a real bang for the buck, unreal value.

Thank you.