Many routers work well with the fiber ONT to replace the Smart RG or Pace Sonic device.
I have tried an old consumer TP-link Archer c7 ac1750--> easy to set up but has limited configuration options.
Now using: Mikrotik hAP AC --> easy to set up followed by unlimited configurations. Small, unobtrusive, good wireless coverage with 3X3 radios and 5 Gigabit Ethernet ports.
Unless you have special networking needs, you may as well keep the Sonic wireless router. You can swap in your Belkin to see how it works and keep it for a backup, though Sonic will quickly replace a failed Sonic router--insurance. I recommend the stock equipment for relatives who have Sonic service--less of a hassle for me to avoid requests for tech support that Sonic can provide to troubleshoot equipment.
Well, my Belkin crapped out so I bought a TP Link C4000 at Costco. It's definitely a lot better than my Belkin was. Pushed my Fusion wifi from 10mb to 12.5mb, my transfer rate from 360 to 780, and my signal % is at 40% now rather than 60. I will swap out the Pace with my C4000 to see which has the stronger signal once I get my fiber install. My neighbors are blasting their wifi channels with 6 Eero on one side of me and the other side has Google Mesh and they clearly have them pushed to max transmission power; in my small house their signals can easily overpower plus I have some lath and plaster walls. The TP Link seems to be pretty darned powerful even against all their signals, and they are literally using every 5ghz channel. Why do two people need SIX Eero in a 1000 sq. ft house?????????