need help with audio connectivity

Your smsl q5 mini amp has a dedicated subwoofer out port mate.

Makes far more sense to just use that instead.

You may find issues trying to run both a USB DAC/amp & the boards sub output at the same time.

Will work fine from the amp itself though

http/www.avaustralia.com.au/polk-audio-psw-110-10-100w-active-subwoofer/

The polk 110 would be ideal for your setup mate , speaker level inputs & outputs.

distortion is a sure fire sign that the speakers cant handle the amp volume
Clipping is the opposite & a sure fire sign that the amp cant handle the speakers.

The polk I suggested becasue it has high level (speaker) inputs, high level (speaker) outputs AND a built in crossover & filter for this cable option.

What this means is you wire the speaker outputs on the smsl q5 pro to the sub speaker inputs.
You wire the klipsh book shelfspeakers to the sub speaker outputs.

When you then set the crossover dial on the subwoofer itself , The sub then only plays frequencies below that crossover setting & passes ONLY the frequencies above the crossover to the bookshelf speakers.

Its powering the low frequencies to the klipsch speakers that is sucking up the wattage from your amp & causing the clipping youre hearing.
Once you remove the low frequencies & let the sub amp deal with them youll have 50-60% more power available for the mid & high range frequencies on your klipsch speakers.

This is the way a 2.1 setup should be run .

Running something like the klipsch sub straight from the subwoofer output on your little amp will push a full range audio signal to both the sub & the klipsch speakers beacuse it has no low frequency filtering built in,not a problem for the sub as it has an adjustable crossover - youll still get clipping on the bookshelf speaker though once you up the volume the same as you are now.
You may not notice it as much simply because with a dirty great 200w sub sat there youre probably not going to run the volume anywhere near as high but its still not the ideal solution.

previous reply was done while you were posting your last one.

You mention a pre-amp now ???