You are getting great advice. I'm slightly newer school than you, LMS320, but I became convinced that I HAD TO HAVE a downscan on my trolling motor when I hired a guide because I was unable to catch anything on my own. With the downscan he said "fish right here" and he was right.
I am partial to Lowrance, no good reason, like ford & chevy. Lowrance has a bewildering array of models and you really have to read the fine print. eg I was going to buy a split scan Hook2 7" and thought I could upgrade by buying a triplescan ducer, but it won't work that way. The unit although looking identical is different so I'll probably go with a Hook2 7" triplescan for the console and a downscan something up front. I'll keep the LMS320 and make it a dedicated map/gps. So I don't need maps on the new ones, the map function makes them about $200 more.
I think that the Lowrance hook2 triple shot is about $200 less than other side scan brands but I could be wrong on that. I'd like to hear what others think.