A bigger rotor rear is excessively pointless, as the rear wheel has far less braking power than the front.
A bigger front makes sense, as the braking power - on decent surfaces - is bigger at the front.
With decent hydros, 160 will be enough for many usages.
and you often find bikes set up 160-160, as 160 has become the baseline size.
it's possible to get 140 rears, to maintain the proportionality between rotor size and available braking power.
If you think you need more braking power, going to a bigger rotor(front) is the cheapest fix next to replacing pads and cleaning rotors.