Power mic's anymore are no longer needed for me in the mobile , I dispise back ground noise period. Mic's tend to match radios and there tune ups or downs , one will sound good on one radio and not so good on another radio.
I like the RK-56 on both AM/SSB , along with stock mic's as well. I think there's a time and a place for a power mic but not very much for me base or mobile. As I said , it all depends on the radios tune up or down (meaning for an amp) Although the 575M6 was a good AM/SSB mic but I never had to turn the thing up rather then to just crack it open.
I tried the Road Devil and didn't like it , it just didn't suit me. I would rather run a 600 ohm coffin style stock mic over one of those. There's just a few variables concerning the mic used and the radio it's on. But then again , I don't want be over modualted to the point of no return either.
The Astatic 636 NC is a good mic as well.