Tactus_au_Rath

I currently have 1.2Gbps service through Xfinity and I currently have a 4 year old Netgear nighthawk modem/router combo which has been dropping internet, so it feels like it's time to replace it. I also currently have two wi-fi extenders, one connected via Ethernet in my basement and another in my kitchen which is not. My router sits in my office which is at the front of my house, so signal strength isn't great to the back of my house or basement. I have two stories + basement, 3.3k sq ft total.

Now I was looking around at mesh systems, hoping to cover the whole house and also trying to actually use the 1.2Gbps I have and future-proof a bit. I have many smart devices, cameras, etc. throughout the house I would connect via Wi-Fi. My computer and NAS sit in my office and would be the main point where I'd want to get the most out of the >1Gbps connection. What I've found is there are very few systems that have >1Gbps ports, and most of them are more expensive.

My current thinking is to get an Arris S33, 3 TP-Link XE75 Pro (1 2.5Gbps port) to run a mesh network and then a 2.5Gbps switch to run Modem > Switch > Computer, NAS and XE75. I don't have much networking knowledge, so would this even work like I'm thinking it will? Would the XE75 Pro make any difference for the mesh network over the normal XE75 with 1Gbps ports?

I currently have a NETGEAR Nighthawk Cable Modem WiFi Router Combo (C7800) that I purchased 4+ years ago with two WiFi extenders and 1.2Gbps Xfinity. I'm noticing every once in a while the connection will be fine but have no internet connectivity and I have to reboot it 2-3 times to get it up and going again. This kind of feels like the last straw as I've been running into signal issues as I am adding more smart devices, so I'm considering finding a good replacement over black Friday.

I have a 2k sq ft home with a basement and I have various devices/cameras/sensors throughout the house, outside and in the basement which I've needed two WiFi extenders to reach everything appropriately. Basement I ran ethernet to, but I don't really want to run any more throughout the house. Router is currently in the front side of the house where my office is - so signal on the back side of the house and basement was too poor for the cameras to run reliably. I have a desktop in my office that is wired, but otherwise there are many devices / smart switches / etc. throughout the house which are all on the WiFi which I'm trying to get better coverage for.

I've been looking around at past threads and I think I'm kind of gravitating toward the TP Link Deco AX5400 with one in my office, one in the basement, and one toward the back side of the house. Price is not as much of my concern as is value and performance - I want what will work best for my situation without going too far overboard. So would this fit well for what I need?

Then my question is how important is a replacement modem? Should I just go with an Arris modem like this? Would I be okay using my existing 2-in-1 in bridge mode or is there a better alternative?