It would be hard to find a 1kw sounder better than the GP1871F/GP1971F in that price range. You won't benefit enough to notice if moving it over to an FCV588. I am not and never have been a big fan of the B164. There are so many better transducer options out there. I would rather lose a bit of the deep water and run the B60 or get a go with something like the B260 flushed into the boat. (assuming this is a boat that goes on a trailer) If you are looking at trying a different brand with the B164, you should try asking that question on a general boating forum where more people have other options. While the B164 has a role, I continue to have it at the very bottom of my selection list. Others will disagree with me, I am sure.