I replaced all my electronics
this year. I spent a lot more than $6000, but some of my experience might be relevant.
As to the choice of maker, I don't think you can go wrong, really. The progress in the last few years is really amazing everywhere. Some people complain that Furuno has fallen behind, but Furuno has its own approach, which is more conservative and more professional-use oriented, which some people prefer.
I have used Raymarine
and Garmin in the past. Which is the most intuitive to operate is a matter of taste. I actually prefer Ray in that regard, and the new Ray systems are terrific, but Garmin also looks very good.
I chose B&G/Simrad for my own new system. For one thing, I wanted the 4G radar. But I was also strongly attracted to the sailing-specific Zeus plotters, and I have not been disappointed. They have a number of unique functions which are really very useful for sailing, and they are very strong in every respect. Besides that, they are very well made and sturdy. I am very pleased, and can recommend without hesitation that you have look.
Because of the greater degree of standardization which we get from NMEA2000, you can now choose whatever instrument displays you want -- they are almost completely interoperable. The B&G Triton displays, whatever other components you choose, are the best thing on the market, especially for sailors, as they have a killer wind
display which shows true and apparent wind
speed and direction in both analogue and digital form -- on one screen
, and completely readable (however, numbers a little small for a big boat). Sound incredible? Best thing since sliced bread.
If you want good radar overlay (not to mention usable MARPA, and pilot performance), you need good heading data. Don't skimp on the heading sensor. I'm using an Airmar H2183, three-axis gyro compensated. Expensive, but worth every penny.
Have fun -- you will be spoiled by choice. To make it even better, prices have fallen drastically compared to a few years ago. An 8" Zeus costs about $2000, although it has higher resolution than the 10" Raymarine
RL80CRC+ which it replaced. Which cost about $7000, IIRC. The 7" plotters from all makers are below $1000, which is ridiculous -- dumping. They must be losing money
on every one.