If you have a surround sound system whose speaker positioning is standard (i.e.
BS.775 compliant or close to it), I'm really not sure full Atmos support would give you a different result than listening to the standard, non-object-based 5.1 stream. My understanding is that object-based audio (i.e. Atmos) only matters if you have an unusual speaker layout or if you have many speakers (height speakers, etc.).
If you can forget about the full Atmos requirement, then your current solution (PC motherboard jack) might actually be perfectly fine, especially if you can't hear the noise floor. I've used using my PC motherboard analog output with my Genelec 8030s for years because I knew it was good enough (verified it myself through measurements). I then switched to a cheap Asus Xonar U7 (similar to a Topping DM7 but much lower class) because I switched to a new motherboard which sadly came with an audible noise floor.
As for EQ/DSP, if you're running Windows you can use Equalizer APO, which is free. It won't be automatic though.