yeah depends on the cash you want to let loose.
the hook 7 cant share waypoints with other units, by a connection such as ethernet or nmea2000. BUT, you can transfer waypoints to an sd card and plug that sd card in another unit and transfer the waypoints to the other unit. takes 3 menu clicks and about 1 minute tops.
as far as NMEA 2000 waypoint sharing for units like the Lowrance elite ti totalscan, yes they will share waypoints AS LONG AS BOTH UNITS ARE POWERED ON when the waypoint was created.
ethernet capable mfd's are the only units that will share and SYNC regardless as well as sonar data sharing and other features, with the exception of the Garmin echomap chirp series which utilizes a seperate 2 wire high speed protocol to share waypoints between their units. the new Plus chirp series uses ethernet and wifi.
waypoint sharing is handy on the bow but if you are in open water and casting to a waypoint, then it is pretty much useless unless you have a heading sensor installed or get lucky by orienting the bow with a landmark to the waypoint.
if it were me i would look at a good unit for the console along the lines of an HDS gen3, helix si, or raymarine axiom if you want to use navionics or other mapping. garmin echomap plus are great units for a little less money but they use their own mapping which is comparable to Lakemaster. they also bought navionics and are merging their cartography data and have added ActiveCaptn to their lineup.
you can still use the 500c for 2d high speed on plane and mount the side imaging xducer up on the transom or on the jackplate for low speed scanning. those big all in one xducers are tedious to get adjusted to read at high speed. what a lot of folks dont understand is that when you adjust an imaging xducer for on plane boat angle, then your image will suffer when scanning at low speeds because the xducer is not parallel with the bottom. hummingbird and lowrance units allows the use of a y cable to add a 2d skimmer to the side image xducer to the same mfd unit. this solves those types of problems.