Which would be better for the Carter, Stevens, Murray county areas? The Uniden BCD436HP or SD100?
Also, would I need any upgrades like the DMR? Should I save my money and get the 436HP Ir is the SD100 the better buy?
They would both do the job. I personally would do the BCD 436 or the 996P2. There is some DMR so you could do the upgrade. I have been using a Unication G5 and prefer it over my scanners. While the Unication has some limitations to me for portability and exceptional receive and with new features being added via firmware you may find it may fit your needs.
None of those counties appear to have simulcast sites, so the 436 would work fine in that area. If you travel elsewhere and want to take your scanner with you, then the SDS100 would probably be a better choice.