(Hopefully this is an easy question to answer - but I'm just getting bewildered by all the different Deco models and features on the TP Link website...)

I have an existing network with three M5s (main one connected to a broadband modem, and two additional access points). It's generally been pretty good, although it's definitely at the limit for the size of our house, and the connection to the two far access points sometimes struggles.

The house isn't huge, but the broadband cable enters in a daft place, right in a corner - so there's quite a long straight line distance, and a few walls and floors, between the main Deco and the two rooms where I want the other two access points to be.

I've also significantly expanded the number of connected devices and wifi usage since first installing the network, with various smart-home stuff and a lot more streaming.

I plan to expand the network by adding an additional Deco device.

I could just pick up a cheap second-hand M5 off ebay, to put somewhere in between the existing ones - but it feels like there might be an opportunity to boost performance of the whole network even more. 

So I've assumed instead that replacing the main Deco with a newer, better model is the best thing to do (and then use the spare M5 to create an additional access point elsewhere in the house.)

My ideal budget is up to about £100 GBP (around 130 USD). I'd consider going a bit above this if really worth it - but equally I'm very happy to spend less if I'll still get a decent performance increase.

So:

• Is there an obvious choice of Deco model that I should just go and buy today?
• If not, what features should I be considering and comparing between models in order to make a good choice?