Discrminator mod to 2006 is by far the most useful...followed by the s-meter mod at a very close second place.
I prefer to use an RCA jack on the back to output the s-meter circuit to an analog meter. It works awesome. You can use this to test for losses in cable runs, aim directional antennas, RDF jerks on ham radio/FRS, detect differences between antennas, determine related radio frequencies when multiple smartzone towers are within your reception range (if trying to find a new site), etc.
I honestly think an automatic P25 decoder board and trunking would've been an option if the scanner was just a little more recent Someone would've come up with a third-party board, or at least some type of CPU upgrade.
Back in the day the 2006 was the king.