Most folks won't take the time to explain why but simply recommend items in this forum, which can be confusing. Let me translate.
The RCA outputs in back you see won't work properly with headphones since they are designed to be connected to either an amp or AV receiver. OTOH, what was suggested is not the correct type of headphone amp (1/4" instead of 3.5mm), and it lacks RCA inputs anyway. Whoops.
If you went with a simple $50 stereo receiver with RCA inputs (sometimes even less in garage sales/closeouts online), you could gain a more flexible & capable device than a headphone amp. A $.50 3.5mm to 1/4" headphone adapter would be the other item needed if you went that route.