I actually have one of my old TP-Link WDR3600 on my friends cable connection and despite the fact its now underpowered for the package they've got, not heard any complaints from him except when its an actual problem with Virgin themselves causing the connection to fail.
I'd always recommend OpenWRT with Cake on the fastest consumer router they can find, for anyone who doesn't have fancy requirements.
I didn't want to use x86 for him as I already had a backup PC up there and it kept failing, he would never go and check on it. Its really not an ideal place as its in a loft that gets HOT in summer, but keeping all the networking up there stops his dad messing with it. He is one of those people who has a nasty habit of pulling cables and pressing buttons while not knowing what on earth he is doing.
I'm shocked its still working as it must be over 10 years now, I'd expect all the capacitors to be failing.