The question for you is: what are you looking for?
A ) A guaranteed very accurate DSSD, go with BK. He will personally inspect and fix everything that needs fixing (gaskets, parts alignment, pearl mod - big deal for accuracy, DW overlay, etc.)
B ) A good shot in the dark - NoobFactory = Cartel = TimesShop whatever the latest model is - Go with Asian clone high beat movements since there's no guarantee you will get an actual ETA
C ) Just something to try on - the inexpensive versions.
I have a friend that has own a gen and has the BK (well it's mine now since he just bought a vintage gen Rolie ). He can't tell the difference unless when you set time and screw the crown because the Rolex movement will do laps around an ETA any day.
Like some other folks said, you may get lucky with the regular Noob version but it's a shot in the dark
If you decide to go with the cheap ones you will have something that resembles but will never pass for a DSSD (the jumpy 21js are a far cry from the smooth Rolex swiping).
PS: Whatever you decide I'd suggest to stick with dealers approved by this board. Some dealers listed above are not approved here for a good reason.