[Closed] 29er disc brake query

Hi,
I want to up grade my current stock brakes on my 29er specialized carve comp, the front rotor is 180mmm the rear a standard 160mm, most of the brake sets I see for sale come with two 160mm rotors front and rear, my question is, do I just need to buy a different type of front brake that caters for the 180mm rotor or do i just buy a standard 160mm pair and then a separate 180mm rotor for the front. I don't know if you can run a larger rotor on a 160mm disc set up. Any help appreciated, thanks guys