I guess Alpine's site has the 4 channel info in the 5 channel's page... typical. Alpine can build nice electronics but ask them to make awebsite and they toss out this crap
http://ecominet2.alpine- usa.com/pls/admn/item_info1a?p_item_name=MRV-F450&p_category=40&p_subcategory=130&p_main=10
You have to highlight the whole address and paste it to get to the webpage
