Hey there, beginner! Welcome to the hobby. Short answer is yes.
What follows is a list, defining each part of a digital audio chain, in the order that your music travels, plus optimal playback tips:
In that setup, your PC (Personal Computer) will serve as storage or streamer, the player, DSP (Digital Signal Processor, like EQ and effects), DAC (Digital to Analog Converter, a cheap one built into the motherboard), and PreAmp. Then, this SMSL will technically serve as an Integrated Amplifier (PreAmp and Power Amp) for your headphones. Why do both this SMSL and your Motherboard both have Preamp function? Because they can both control volume, and that will affect the quality of your sound. Keep in mind that there is a spectrum of quality for each component, from your headphones to the type of files in your storage/stream.
Basically, what you will want to do is connect your SMSL amp into your PC’s 3.5mm headphone jack (or RCA if it’s there), set windows volume almost to max, and start the SMSL volume from low and adjust as needed from there. The lower your PC volume is set, the more music data is thrown away and the closer the music signal will be to the “noise floor” of fuzzy hiss in the background. The more you have to turn the SMSL volume up, the more it will amplify your computer’s hiss, and even a little hiss will collapse the sense of soundstage depth in your headphones.
newbie here - i have the SMSL SU-8S as well - am I supposed to connect amp to the DAC via XLR cable? If so, does that mean I'll need to unplug/replug every time I'd like to use my studio monitors connected to the DAC?
The SU-8S has an XLR and RCA output - wondering I should just use the RCA instead for this amp.
If I remember correctly you get output from both xlr and rca.
So if you are already using xlr for something then just use the rca for the other.
Not advisable to use a (cheap) switcher as that can introduce noise.
This has more than enough power for the 6XX. Tests on youtube has suggested that you can throw very expensive dac's at it, and it will respond with better sound because of its high resolution and great power.