It's also okay (and easier) to just pin the cable to the corners of the wall using cable holders. Some will not like the 'look', but generally speaking if you're willing to accept a more raw/industrial look it's not bad to do it that way. And its really fast compared to powerline.

Replying to your comment on hacking/drilling, just to say it's not always necessary.

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.