i wouldnt recommend hpr for your downpiping cause they dont do exhaust work , they'll refer you to another person who does all their exhaust and piping work,
so here's my suggestion.
come to f10 , get a 2.25inch downpiping made by one of the exhaust dudes there , that'll be for around 3000 , for the header , you can either buy or order a branded header , that'll be 10000+ , the ones that are chromed from the inside , those'll actually increase hp.
or the other taiwanese and malaysian made unbranded headers , those'll be in the 6/7000 range .
other than that , its your choice