AiMesh can be decent enough, and as
@OzarkEdge suggested, I'd assume you've done all you can do to make it work for you? If so, and you're still left desiring more performance and or better client behavior in whatever way, there are way more robust options for distributed wifi, especially with a $500 budget.
That said, we need to confirm if you can get away with a wire-first/wire-only (WFWO) system, or if real mesh is necessary. The main question to answer: can you
wire in all of your APs (via ethernet or MoCa)? If you can, then non-mesh centralized wifi would probably work well enough; stuff like regular UniFi, TP-Link Omada, Cisco small business WAP, etc. If you have to backhaul one or more APs via wireless, then you will likely want a true mesh product: Eero Pro or Netgear Orbi for consumer, UniFi Mesh for business grade, or for really-mature enterprise stuff where all core 802.11 protocols tend to "just work", Ruckus or Aruba.
Without knowing your constraints or any other specifics such as internet speed, number of clients, bandwidth goals, etc., I'd
personally scrap the Asus stuff, drop in a $60 Ubiqutui ER-X as your router, a sub-$100 web-managed PoE switch and invest the remaining $350 into wifi. Again, if it were me, I've grown to have
zero patience for anything less than stuff that simply works as intended, so I try go with Ruckus every time, even if I have to go working-pull off eBay. If that's me being a fan boy and/or it's deemed total overkill, well then so be it, but the stuff simply outperforms anything else I've ever tried in most any real-life situation, especially when interference could be an issue and/or density is high, plus they seem to require fewer APs per LAN. And for anything from the R_00 units onwards, you can run them without needing a separate controller (yeah, I'm looking at you, Ubiquiti...) via the Unleashed firmware. I'm sure other systems like those I mentioned above would work well enough, presuming you've done your due diligence and know what capability you're buying into (and not).
Hope that helps!