Pfadt seems to make good products. I have Pedders on my car and I am very happy with it. They have been very good to deal with and a lot of information provided on why they make the parts the way they do.
'10 CTS-V : LPE 650+ Package 587hp / 582tq
2.55 Upper / 8.6 Lower / ID850's / Kooks Longtubes / New Era CAI