Better to ask than guess and be wrong, so no worries.
Some people try and cheap out with a FWD car and only get 2 winter tires. They probably make it to spring in one piece because the front tires do both the steering AND propulsion, so they think they're fine. However, were they to go around any corner at moderate speed or above, they'll likely find themselves in a spin rather quickly since the rear has no grip.
On a RWD car, there are no excuses for only using 2 winter tires. Without winters on all 4, you'll accelerate just fine...and then have trouble steering or stopping. Your call, but tires are one place you do NOT want to cheap out on. Only part of the car that touches the ground. Without good tires (winter OR summer), your 400hp are useless.
Completely agree. Over here in Germany it's mandatory to have all four snow tires the same. Actually, if you've ever drivein a RWD car in the snow you will know immediately that having all four good snow tires makes all the difference in the world.