slant 6 exhaust

I was thinking of doing an exhaust 2 1/4 on my slant 6 for a lil boost in power. and sound. i am wondering what is a "fair" price to pay to have it piped, also someone said about drone? the muffler i have and would like to put on is a flowmaster 40 series single in dual out it is ( 2.5) but that can be changed, or should i stick with something more subtle thanks for the answers guys!