I will curtail this before it gets out of hand, which it surely will.....
Monitoring CONVENTIONAL (non-trunked) analog and digital channels is not difficult at all, and any radio XTS3000 or XTS2500 can be programmed to do so in receive-only mode. You can scan 15 channels plus the selected channel.
Monitoring TRUNKED analog or digital talkgroups in receive-only is a whole other story. With the XTS2500, it is a no since Astro25 radios must affiliate to unmute to any traffic. There is a way to scan and filter talkgroups in conventional mode, but it is tedious and not an ideal solution. XTS3000's can be programmed for receive only, but only by someone that really knows what they area doing. If you are talking about monitoring STARS talkgroups, the XTS3000 is out anyway since they do not support 9600 OBT trunking, 800mhz only. Best to stick with a scanner for trunked systems.