Best Air Parcel Shipping Rate from Canada to Korea?

this is for about 1.5kg weight box
the size of about two shoe boxes

to be shipped from Canada to South Korea
registered, preferably with tracking
to be delivered in about a Week .

problem is that I've found Canada Post (Xpress or Priority) to be quite expensive
compared to USPS Priority international
(who would charge about USD $30~40 for above)

does anyone know any other courrier service
with better price between this route ?

- Thank You !