No consumer router can truly cover double storey homes. I bought a cheap router to cover my first floor, connected via powerline adapters to the main router downstairs. Luckily found out my built-in phone lines can be converted to ethernet ports, so I will do that when Unifi turbo upgrade comes.

Do u have a router eg stock one given by TM? If yes, you can bring the stock router upstair and add a decent router + powerline adapters. Tenda AC9 + TP-Link PA4010 kit will fit your budget.

Do you have built-in TV antenna points?

Spec-wise & reliability-wise looks ok for Tenda. But don't buy Tenda if u wanna install other firmwares eg DD-WRT.

I see your electrical wiring might be abit noisy hence not-so-good Powerline performance. Do you have inverter air-conds in the house?

If u have co-axial points, you can use co-axial to ethernet adapters. Around RM 100 I think.

Best option is to bring an ethernet cable upstairs but a lot of hacking & drilling is required.

Do you have built-in telephone lines?

Otherwise your best bet is to use at least AC1900 class router.

Agree. Not everyone can accept the ugly look. But u'll get full gigabit speed in return.