I didn't. For a dedicated streaming pc you really don't need much except a somewhat modern CPU. I bought a used HP pc off of amazon for ~120 bucks. It has an I5 in it. I also bought a cheap capture card ($18) which streams perfect 720p -1080p. I use CPU encoding on the stream pc. Works like a dream. You can check out my most recent broadcasts at twitch.tv/dewy_ttv if you want to see the quality. I stream at 720p but i'm a really small streamer and my bandwidth isn't great. I also use the VBAC banana mixer for audio.
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PC I bought (I got it cheaper since it was used) https://www.amazon.com/gp/product/B01GKC21GC/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1
The capture card I bought doesn't seem to be sold on amazon anymore, but I bought one like thishttps://www.amazon.com/MT-VIKI-Capture-USB2-0-Camcorder-Streaming/dp/B08G15Z4KY/ref=sr_1_12_sspa?dchild=1&keywords=DIGITNOW+Audio+Video+Capture+Cards&qid=1607893617&sr=8-12-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFIM1NMVE1NOUdTNkwmZW5jcnlwdGVkSWQ9QTAyMzA4MTBEUTFTTjlZNVZQQSZlbmNyeXB0ZWRBZElkPUEwNTczNzg0MjVEMldHU0sxWE5IRiZ3aWRnZXROYW1lPXNwX210ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=