I had a thread going on this fairly recently... I had a good 7” garmin with chirp to begin with, which gives a great image, but no charts. I picked up a Samsung tablet and mount for under $300 combined and with navionics. Now I have a 7” fishfinder, a 10” map and an iPhone 8+ to boot. Screens galore!
It’s great now and I’m very pleased with the results, but if I could have a redo I would’ve just got a good 10 or 12” HDS from the start.
There is also a great deal on a new in the box garmin right now on the buy/sell/trade forum right now for well under half of the retail. I almost snagged it myself, but I just finished getting my other stuff all dialed in.