You need to replace the MFD along with the Radar. So the least cost option is the least cost MFD and Radar combination you can buy on the market, and it should be Raymarine
because then you have the capability to control your existing X-30 autopilot
without replacing that too.
Now you mention that your autopilot is on SeaTalkNG, how are your other instruments (wind, depth
, speed, etc) connected? Are they SeaTalkNG also? Or are they older SeaTalk1?
For anything older, like SeaTalk1, you will likely need to add a SeaTalk1 to SeaTalkNG or SeaTalk1 to NMEA2000 converter. But we'd need to know more about all of the components and how they are all connected. Ideally a wiring
diagram showing how each component is connected would be drawn up and then a pretty simple solution can be made from that.
In any case, a small Raymarine
Axiom and any Raymarine Radome is the starting point. The rest is just a few components for interconnecting what you have on the boat
with the new MFD.