You can get many excellent tires for half of that.
is it ok on a awd car to mix tires have 2 different brands on the car as long as they have the same ratings ?
Generally no. Even if they have the same size marked on them, the actual diameters can vary quite a bit from brand to brand. Plus they will have different traction, braking, cornering etc characteristics ...
So, in summary yes you need 4 new tires.