I am one of those people who just got rid of the Garmin system on my boat and replaced it with Furuno (which is what I had for many years previously). I have over 25 years experience operating recreational radars and I will say flatly that Garmin is just not very good at designing or producing radar. I had a 25kW 6 foot open array so my experience is limited to that and may not apply to their dome units or their solid state radars.
In three years, I had to replace the pedestal twice due to hardware failures. It was handled under warranty but not exactly a positive sign. When I first got the Garmin radar, the sea state and rain filters were so bad that they were almost useless. When set high enough to reduce the noise on screen, they also filtered out many targets. So if it was raining or the seas were rough, you had to tolerate a lot of noise on the screen to see smaller targets. This was greatly improved by a software update about two years ago. The auto tuning on the Garmin was useless and also produced settings that lost targets.
What I found in the end was that with fully manual tuning, I could get pretty decent performance out of the Garmin 25kW open array. It was fine for navigation. By comparison, on my old boat before I got the current one that had the Garmin system, I had a Furuno 12kW 4 foot open array. That radar on full auto was vastly better than the Garmin even at its best with manual tuning. I could see flocks of birds 4-6 miles away, which the Garmin could never do despite having twice the power and a bigger antenna array.
I just got my boat back with the new Furuno equipment, which includes the new high power solid state DRS25A-NXT open array with a six foot antenna. I have only used it for about 8 hours but it is night and day from the Garmin, it is so much better. It can be left on full auto and frankly it's hard to do better with manually tuning it. I am extremely pleased with the DRS25A-NXT and very happy I switched.
So in response to your question I would say this based on my experience. If you do feel budget constrained, given your uses for the radar I would leave the Garmin on board for now and spend some time learning how to tune it manually (and make sure it has the newest software). Perhaps in a year or two you can swap out for a Furuno open array. If you want to have the flexibility of fully networked displays, sell the Garmin stuff but recognize that if you go to a dome, even a though it is a Furuno dome, you will never equal the performance of a large open array even a Garmin one. What you will get with a Furuno dome is a very good navigation radar that works well in auto mode, unlike the Garmin. That's a choice only you can make given how you expect to use the radar and the rest of the electronics.
