yea. PE sells it. i'd post a link, but i can't post link's from a wii. //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif
I doubt you'd need it unless you like building fancy passive setups...i use to build some awesome single amp setups...using passive networks back in the early days of car adio when there was a 50watt and 100 watt power class
a basic car audio book will give you plenty of info...i use to use a book from PAC they use to sell a lot of different coils and caps.....the book was informative on different slopes....and the coils and cap needed