Hi Pete,
Welcome to the wonderful world of boat ownership π
As for your question, I have no direct experience of the Raymarine kit, but I can suggest that for the vast majority of anglers, we do just fine with Chirp, Down and Sidescan views. It's easy to spend a lot of money quickly, chasing the next best thing in sonar imaging but I recommend you go for regular chirp/down/sidescan and learn to use it effectively. You'll find that it's perfect for 99% of our fishing here in the UK.