I have the SEG and it definitely isn't aggressive. It's one of the sweetest DACs I have. However I have both the GFU (previous version) and SEG and one of the little SMPS they came with injects some noise into the left channel (iirc). The other one doesn't. This is only noticeable on the SEG, not the GFU, and I'm not sure which one it was. I think they're the same model so it's probably just unit variation. I use a linear PSU now anyway so I've not heard it for a while.
Aggressiveness was also a feature of my system for a long time until I found the right mains filter, with a Furman LIFT filter being the first I found to tackle that particular issue. My mains has been much more friendly recently, as determined by another unfiltered system, so it's something that comes and goes. I know a lot of people are using batteries to power DACs which also works. If your soundcard is running off the ATX PSU then that may be much better filtered.
I've also installed a lot of acoustic foam in my listening room as it was very live previously. In hindsight I could have just switched the dining and living rooms around as the dining room is much better behaved, but the foam is glued to the walls and ceiling now. Until it falls off from the heat.