If its a CX or DX that has the cat IN THE HEADER itself then yes it matters alot. you cant just swap another header on it like an aftermarket one. The CX and DX and IIRC some of the HXs have the catalytic converter located up top right off the exhaust manifold flange. If you have one of these types of manifolds you have to

1) Find a direct replacement because your O2 sensors and your exhaust manifold is sepcific to the car

2) Change over to an EX style setup which means buy an aftermarket manifold, aftermarket cat, and extend your O2 sensors to the EX locations and have an exhaust shop cut an weld to make everything fit.

If you have an EX your catalytic converter is located downstream and you can replace the header if it is cracked.