I'm still using stock router supplied by TM (TP-Link Archer C5 AC1200) and now turbo-ed to 300 Mbps. The router is located on the ground floor but unfortunately my main PC is on the 2nd. I can only get around 80-110 Mbps through 5 GHz using the TP-Link Archer T4U. Also, around 70-100 Mbps on my iPhone. On the ground floor, I can fully utilize the max speed (300 Mbps) with either 5 GHz or Ethernet LAN.

My question is, do I need to splurge some money to replace the router with something that would allow me to still get 300 mbps through WiFi on my 2nd floor or is it not possible or just plain waste of money?

Thanks a lot for the suggestion. Appreciate it.
I also thought that too that 5 GHz won't be able to penetrate multiple walls for full bar coverage which makes me curious if any more expensive router could be able to do so.
But now I'm thinking how to drill the wall for extending the LAN cable to 2nd floor without making a wire mess on the wall

Does anyone ady done that neatly? Mind to share your experience?

Yeah, maybe the improvement would not be significant.
I just thought paying for 300 mbps but only can utilize less than half of it most of the time. This was never the issue before the turbo frenzy tho (last time only max at 30 mbps so even cheap router can give that speed)
But now we're moving to much faster and better internet experience but I guess no point of replacing the C5 for now just for a little faster WiFi speed on the 2nd floor
I also just received offer by TM to upgrade to Ultimate pack by adding RM10 monthly so now only pay for RM159 so downgrading to Unifi Lite 100 mbps seems not worth it at all