I am going to install a Kenwood MP3 player deck in my Dakota soon. I also plan on installing a alpine amp to run a 12" sub. The question I have is, is there any real difference between the amp install kits that you see on ebay for $15 or the kits you see in stores for $100? I have Monster cable RCA's, so basicly, Im looking for a power wire & a fuse block only. Also, I need a small box for the sub itself...Should I buy a pre-made one or make one myself? If I make one myself, how can I get the dimensions that I need to use? Thanks Fellas.