https://www.amazon.com/gp/product/B06XPRDVDC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Ended up going for this (32x8) as the SB6183 is still (16x4). I ended up going with an AC series TP-link router because frankly I don't own any devices that can even use anything more than Wifi 5. https://www.amazon.com/gp/product/B07N1L5HX1/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Ok, I may go that route, thank you for your help. But they're not cheap, so I have another related question: Can I just turn "Wireless Radio" to "Disable" in the wireless setup of the PK5000, buy a wifi router, like the one listed below, and plug it in via Ethernet cable to my PK5000? If it's only the wifi portion of the modem / router, this should help at least diagnose the problem, correct?
Sub $150 Docsis 3.1 is still a ways away.
The modem is what actually lets you use the signal from Xfinity to connect to the internet. The wifi router allows you to use wifi to be able to access the internet instead of having to be connected directly to the modem or wifi router.
You really only need Docsis 3.1 modems with Xfinity if you have internet speeds beyond around 600 Mbps.
Buy yourself a DOCSIS 3.0 modem as there are so many cheaper options
Modem https://www.amazon.com/MOTOROLA-Certified-Comcast-Spectrum-BrightHouse/dp/B01A1E6BA2/
Router https://www.amazon.com/TP-Link-AC1200-Smart-WiFi-Router/dp/B07N1L5HX1/
A budget of $35 is certainly not going to get you wifi 6 with great speed.
The only devices I can say anything at all about are TP-Link routers and APs that have the hardware of the Archer C6 V2 in it: https://openwrt.org/toh/tp-link/archer_c6_v2
While they won't blow you out of the water they are decent enough for the price.
Found a refurbished one on Amazon: https://www.amazon.com/TP-Link-C6-802-11AC-Ethernet-Wireless/dp/B08H75LG8S/
But the A6 V2 should be the same as the C6 V2 just rebranded for Amazon and should take the same firmware from what I can gather online: https://openwrt.org/toh/hwdata/tp-link/tp-link_archer_a6_v2_us_tw
https://www.amazon.com/TP-Link-AC1200-Smart-WiFi-Router/dp/B07N1L5HX1/