I've had problems before using my 396XT monitoring both the Butler County's Simulcast, and Sedgwick County's system as well. The problem is less when monitoring Butler County because I live in Andover, and the closest tower is right over by the KTA entrance, so I'm not dealing with multiple towers with the same relative signal strengths. Not so for Sedgwick County. The 396/996 can hardly do much with it.
I've had a 436HP since July, and it has done a much better job handling the decoding of received P25 data. Look at your 396's screen while monitoring Butler County Simulcast for example. You will see it may switch around a lot between NFM and 851.425. It may pick up a TG grant, but when it switches to the voice channel, it may just say LNK when it should be decoding voice. You can thank the manufacturers for the way the products are designed. The 436/536 are both great improvements in overall performance on both systems, I can attest to that.
Now with all of that said, if you would like the best performance, you could purchase an XTS2500/5000 for RX only trunking. I'd only do that if you know what you are doing. If you understand, it's not that difficult. Don't do it if you have no idea what you are doing going in because you could screw up and accidentally have your radio attempt to affiliate with the system by selecting a TG. It works by basically slaving a TG to a conventional channel in a scan list, and placing the TG in the same zone but higher than channel 16 so you don't select it. You could add multiple TGs to scan at a time, but know that you are limited with what you can do. It's worth it to me because half of the channels aren't used regularly anyways. For example, if you wanted to monitor Butler County, you could get by with these channels:
-BU SO 1
-BU SO 2
-DPS 1 (Augusta)
-BU EMS 1
-APD 1
-APD 2
-AFD OPS (May respond on this channel, or an Event Channel)
-BU Fire
-Event Channels
-Event Channels 1&2 are what you would normally need; Event 7 for Andover Fire
-Event 8 has been used by Andover for GAD (PD/FD)
Now you could expand KHP into that if you wanted, you can always make different groups depending on what you are wanting to monitor at the time. If you in to listening to lane runners on the KTA, listen to Troop G or KTA..haha.
Jacob