Keep in mind that rotors are not all just about size, or the outer diameter in this situation
You also need to consider the number of vanes, width of the ring, total thermal mass, just to name a few.
For example, my Brembo 365 mm rotor is actually heavier than the StopTech 380 mm rotor by 4 pounds.
The stock rotors, although similar in weight compared to the BBK rotors, have only 30 vanes each, vs. 48 for StopTech 355 mm rotor. This is a main reason, at least in my opinion, why the stock rotors don't cool as well as the BBK rotors.
Hence, even at the same size (diameter), two rotors can perform drastically different depending on how the vanes are designed. So don't be blinded by size alone.
FYI the European AP kits (which is what you've been looking I think) are slightly different than USA AP kits. That's why very few have heard about 378 mm AP front kit here.