[Closed] What WiFi router?

Having extended the house the router is struggling a bit to give a decent signal everywhere. As it was the free one that came with our broadband about 5 years ago I'm assuming it's not the best. Seems sensible to upgrade this before I start adding range extenders and the like.

Are they much of a muchness or is there something I should be looking for? I've got a few wired devices so I'd like to keep that feature. Ideally 6 ports but could live with 4.

Not too spendy or something I can pick up 2nd hand is fine