Other options I'm considering on this set up are:
Get a Garmin 557xs with TM150M CHIRP transducer instead of the Furuno. This gives me a better GPS than the Humminbird with maps but I'm not sure which is a better sounder for my purposes.
The other approach is to get a Simrad NSS8 with Lowrance Structure Scan and 83/200 transducers and just have the one unit.
Price is about the same for all three setups so I'm looking for peoples opinions on any of the above as I'm unsure at this stage.