As mentioned earlier, don’t do any internal mods as you have a nice amp. Some simple things are use a good heavy gauge high current power cord so you don’t starve your amp. If you’re using a $2 spec grade wall receptacle, upgrade that with something with better contact pressure to a Hubbell hospital grade outlet, which you don’t have to break the bank on that. Next if you’re really looking for an improvement and own your home, run a dedicated circuit or two your system. Isolation isn’t a bad thing to work on including your rack, but something simple and affordable are Cardas myrtle blocks… they work.
If you really want to improve you’re system, since you’re running your RME direct, is toss the switch power supply and get a Teddy Pardo, SBooster or other linear power supply as this will make a big difference.
Room treatment is also a smart move but most don’t want their room, especially if a great room or shared living area looking like a recording studio but it is probably the place to start or your chasing your tail. Great amp… enjoy it.