I am having a number of routers in stock. Linksys WRT3200 with terrible WiFi, Asus AC3200 with Merlin WRT firmware (its WiFi is faulty), GL-iNet B1300 (with poor WiFi on 5GHz).
I want to switch to a powerful router than can spread WiFi signals across concrete walls, repeaters have not been a good idea in the past.
Besides that, I want 5Ghz clients to directly connect to ISP (no Wireguard or OpenVPN) and any client connecting to the 2.4Ghz band to connect with Wireguard (with Wireguard client set up on the router).
You do realize that concrete walls are a death penalty to 5 GHz signals, with 2.4 GHz not faring that much better?
The only sensible solution in such an environment is to rely on a wired backhaul as much as possible (ideally ethernet, maybe powerline if you can't avoid it) and to use small/ low-power APs from there (~one for each room). Only if that really isn't possible, triple-radio devices ('mesh' in commercial terms) might a (worse) alternative, but even there the keyword is 'multiple satellites', not 'one strong AP' - you can forget that boxed up in concrete.
Honestly it isn't a big place but signals get weak and I can't do wiring. Tried having router (on PPPoE) in the middle of this place and had it connected with CPE via powerline adapter but then speed deteriorates and I get 1/5th of speed.
You could probably look into something like a MoCA network adapters. These runs off your TV antenna sockets.
I do agree with slh's point on how concrete walls are a death penalty for 5GHz, not to mention the fact that 5GHz is already very limited in range for operating in such high frequency.
What you might also want to look into are 2.4GHz outdoor APs, these may help penetrate through the concrete walls better, despite being mostly directional and operates on single band.
You also need to take into consideration that most clients are capped at 20 dBm, so even if the AP would offer real 30 dBm, the clients would still struggle to get the data back to it.
As long as you can "mesh" them around your walls, you can pick up three used Linksys EA8300's (extra radios for mesh) and stay within about half your budget. Almost worth just trying it at that cost. These are four core IPQ4019 SOC's - not bad hardware at all. @Jeff uses these. He'll probably chime in shortly
