i need to buy a firewire cable solely to charge my new ipod. i've bought an adaptor for my 4g ipod that will plug into the dock connector. the adaptor will allow me to have a line out that i can plug into the stereo. i'd also like to be able to charge my ipod while it plays, so i need to buy a 6pin-6pin firewire cable that will run from my ipod's adaptor to an exisiting apple power adaptor that i have. apple charges $20 for a firewire cable, but i find multiple places on the internet that charge only a few dollars for their cable. is there any reason for me not to buy the cheaper cable? i won't be using this particular cable for data transfer, solely for charging my ipod when i play it away from home.