So many audio review sites you could check out but tbh anything from a reputable brand e.g. kenwood, alpine etc will be decent. Higher end stuff like jl audio (not jbl), boot on acoustics or focal are good quality pieces of kit.
Avoid halfords brands like fli or boss.
No speakers are a straight swap as the car uses a specific connector. All you have to do is cut off the connector and crimp on some spade connectors for the new speaker terminals though.