alexatpos - In the future I may be more interested in upgrading my sources, but as I mentioned in my first post my system is absolutely limited by setup and I can honestly say that I've heard very little difference, if any, among the various sources that I've used. The difference between the Krell and Pathos, on the other hand, is quite obvious.
The other source that I am currently using is a Bluesound Node 2 through a Maverick Audio TubeMagic D2 DAC that has all of the offered upgrades. I consider the SACD player to be superior simply because it has SACD capability, but the solid state output on the DAC sound identical to Redbook CD to my ears.
One thing that is interesting with the DAC as a source is that with the Pathos the difference between the tube and solid state outputs was simply a slight softening on the high end which I almost never preferred but didn't find objectionable. I used it at time for general listening to take the edge off since my wife is volume sensitive. With the Krell, the tube output on the DAC sounds awful to my ears. I ended up putting a splitter between the DAC and Pathos and Krell so that I could use the solid state output for both. The DAC is my casual listening source and the SACD player is directly connected to the Krell currently for best results.
You've probably picked up on the numerous less-than-optimal things in my systems ranging from the physical setup on the speakers to having a switch between the amplifiers and speakers, and splitters in the source connections. I can certainly see how one could be driven nuts if the system was able to be setup optimally where it was easier/possible to really evaluate the more subtle differences in components and such. Maybe a blessing in disguise for me...