I'd check out the PC to see if it was using HDMI to the monitor. Then I'd setup the usual receiver with that and disable the sound blaster. I'm sure you read http://www.tomshardware.com/reviews/high-end-pc-audio,3733.html so I won't discuss why we know not to stick with any particular sound card.

https://www.amazon.com/Best-Sellers-Electronics-Audio-Component-Receivers/zgbs/electronics/14269301 is the usual. I didn't find any sub 100 buck unit. My bet is that while you can get a fine stereo receiver for this you'll have to go ebay.