If, by asking about an "unlocked" scanner, you are referring to receiving encrypted channels, that is never going to happen. It's illegal, so no scanner manufacturer is going to push their luck.
There also are no available scanners that are unlocked as far as cellular telephone frequencies are concerned. That's also illegal in the U.S., plus cellphones now use a digital format unreadable by scanners.
For your theoretical $1500 budget, as K4EET noted, you could get an SDS100 (handheld), with the DMR & NXDN upgrades, with a lot left over for either future use or antenna & cable upgrades. If you mainly want to use any new scanner as a base, at home (not portable), then I would suggest getting the SDS200 instead., along with the DMR & NXDN upgrades. I would not advise getting the ProVoice upgrade, as that system type is no longer supported, and most current users are migrating to something else, many to P25 Phase II in my area. Also, I did not see any ProVoice systems in use in your county, nor in any of your adjacent counties. There are a number of DMR users in your county, and some NXDN in neighboring areas. There could also be one or more NXDN user in your county, but nobody has analyzed their system & submitted it to the database. Your 436HP can also be updated for NXDN and/or DMR,
Which system are you seeing, on which scanner, where it stops on a channel, showing P25 but no audio? If that is the WS1040, on the P25 Phase II state system, then as already noted above, the 1040 cannot decode Phase II.
