If you have 10 year old units, you got both some catchin-up-research to do AND a culture shock to prepare for regarding prices...especially if you want to network.
I used to run 'birds - nothing high falutin', 5' screen monochrome but was not unhappy with them - good sensitivity. When I lost one of my Garmin gps units to water intrusion, I couldn't do without and shortly discovered that stand-alone gps units were pretty well a thing of the past.
I went to shop a 'bird 397 (combo gps-sonar a/COLOR) since I was extensively familiar with the 'bird architecture... and ended up getting a Lowrance Gen2 non-touch which was similiarly featured plus a $100 rebate that I admit made me look twice.
You didn't specify what sort of network...Ethernet or NMEA? They do different things.
I can tell you a little of the good, bad and the ugly on Lowarance HDS.
HDS exists in multiple versions since 2010: Generation 1, Gen2, Gen2 Touch, Gen3, Carbon and currently HDS Live. The line is both Ethernet and NMEA networkable. Gen1/2 were a 4:3 aspect screen in sizes 5, 7, 8 and 10 inch. Gen2 Touch and later are wide screen format in 7, 9, 12 and NOW 16 inch screens. Depending on screen size, they can be split to show 3-4 different functions on a single screen.Gen1/2 have modules available to add down/side scan (with added transducer) while all Touch models have capability built-in. There was a I think a 360 Scan 'ducer that didn't near pan out the way they claimed - started out at $500 and by the time they were done, they were giving them away with units (for free). There is a 3D scan now and newest (it may or may not be released yet) is the LIVE 'ducer which also maps the bottom as you go (and displays on screen).
At the top end, the 16" HDS Live sells for about $3,300 w/o 'ducer. If interested in the HDS line, I might suggest looking at the used earlier generation units unless you want to spend significant bucsk. I run Gen2 (non-touch) at a price-point I could justify (4 units w/side-down scan front and rear). Of course, if I had known the info that follows before I bought my first HDS, I'd have probably bought the 397 'bird... But, I'm in it now and so far, so good. I'm not investing in newer versions though, for sure.
The good is many capabilities: color, resolution, networkable (e-net/nmea 2000/0183, multi-sonar options, Sirius/xm, radar, engine functions, gps with built-in mapping (Insight), SD/MicroSD readers.
The bad is it's basically a computer: Lowrance issues updates (much like Windows) here and there - sometimes they add functions, sometimes they fix functions AND sometimes they delete functions (like when they deleted the ability to log sonar/gps info that could be sent to Navionics to be incorporated in their SonarCharts feature to make more accurate maps). Sometimes the updates cause more disfunction than what they fix. Touch screens that sometimes don't function well when wet. Of course that's better than having a unit fill with water... After all, who fishes in the rain? The menu system is much less intuitive that 'bird - in my opinion/experience.
The ugly is that Lowrance warranty is lacking - 2 years and done. During that period if your unit goes in for warranty, the likelihood is you will get somebody else's (used) unit back that they fixed - your unit isn't fixed and returned (they claim they don't repair units). So understand under warranty - you will be sent a used unit. After the 2 year warranty and you have a problem, you're ship-outta-luck. Remember when I said that they say they don't repair units? They have no (admitted) facility to repair units....will not fix. Even though they ship out repaired units for warranty claims. IF you get the RIGHT customer non-service person concerning your out-of-warranty unit, they MIGHT offer you a few dollars off on purchase of a new unit. Customer support can be a challenge talking to people in Asia minor. Whoopee
And I won't go into their rebate "racket"
Have fun researching/shopping.