When I visited family in the Twin Cities area, my SDS 100 (and 200 in my vehicle) worked splendidly! I've tried monitoring the ARMER system with scanners as far back as the 796 model and the simulcast was quite frustrating with them.
Simulcast systems, as you find in the metro areas, can be very daunting. You are very fortunate to have good reception with your Icom.
If you are not in a metro area using simulcast, there is no reason to get rid of your 436. Some of my travels had me in the East Grand Forks area and I had good results with the x36 and x96 models. (But they weren't very active either as small towns are kind of quiet.)