I built a PC a few years ago for college work and light gaming. I used an ASUS B-350 Tomahawk motherboard and recently decided to start making upgrades to the build and in the process decided to get myself some fancier peripherals and devices I never had before since I am now working full time and wanted to use this more as a place for rest and relaxation.

I purchased myself a monoprice desktop amp and a pair of DT 990 Pros having seen this exact set up and similar set ups get some great reviews. When I went to upgrade my set up today I realised that I couldn't get my new headphones to work and I have struggled to find anything online about my specific issue.

The amp itself has an L/R audio in and the cable that came with the amp is L/R to L/R but I cannot find any configuration on my motherboards native audio jacks that produce the correct audio when I use an online L/R test.

Based on the above I have some questions.

1. Is there anyway I can directly connect the amp to the motherboard and get the correct output?
2. If I were to use a splitter to connect the amp to the motherboard would I see a decrease in quality?
3. The amp also supports USB audio but I have always been under the assumption that analogue audio was superior and I would also like to keep my remaining USB port free. Based on my situation is it worth using the USB port over the audio jacks?
4. Would a cheap sound card allow me to connect directly?
5. Which of the above scenarios should theoretically give the best audio quality?