I am thinking of purchasing an ICOM IC-R6. I want to monitor mainly the AIR BAND including the HF Oceanic and Gulf of Mexico routes. I also may want to monitor the HF marine bands will the R 6 do this? Thanks in advance.
The R6 does not have SSB capabilities, so you wouldn't be able to monitor the HF routes.
If you wanted that capability in a handheld, then the R20 might be more suitable. Even then, on large HF antennas, the R20 can suffer overload, then relying on attenuation to keep it under control.
Your best bet for monitoring the HF routes is to pick up an HF-oriented SSB capable receiver.