Using a PS3 - which router

[Zimmerman]

My mate is in to his gaming (COD predominantly).

Been getting dodgy speeds/performance.
Has been using a post office issued router that's at least 8 yo.

Speed test look reasonable (around 18mb download from memory).
Earlier today it did drop to <1mb (but I think that was a blip).

But I think the seed was sown a few weeks back when someone suggested he got a better router...today has just reminded him. In fairness, the current one is 8 or 9 yo... So has there been any technical advances in the world of routers?

If looking to replace his router is there anything special he should look out for? I've probably got 2 or 3 knocking around my house, but will they be suitable?

Bear in mind he's the sort of guy that has spent about £170 on a controller... So he takes his gaming seriously.