Looking for advice and recommendations on how to have a proper 2.1 audio setup and headphone setup

[TheReclaimerRx7]

Hi, so currently I have a pair of passive bookshelf speakers and a passive subwoofer that is being powered by a car amp using a xbox one power supply. It is then connected to my pc with a 3.5 mm cable. Every time I turn it off it makes a loud constant hissing noise, so I just unplug the power cable and turn the whole thing off. I also have a pair of audio technica ath msr7 and Philips fidelio x2hr, I would like to know if I can buy something that would make it easy to connect my 2.1 setup and headphones into and have that connected to my pc? or would it be best to ditch the car amp and xbox power supply and get something different? Sorry im noob to these kinda stuff. my budget would be 150 to 300$ Thank you so much!