Cabelas has the lowrance HDS-7 on sale for $599 after rebates from Jan5-16. Just checking with you guys that already have them to see what extras you have to buy and how much. I know you have to buy the side scan seperate and didn't know what else was needed. Will this unit interfere with my Hummingbird unit on the trolling motor if both are left on at the same time? Do you think lowrance is coming out with a new model and that is why they are discounting this unit? Thanks for the information.