Bachmann’s RS-3 runs quite well and offers more room for sound. I did a very basic sound upgrade years ago, hardwiring an MRC decoder meant for a standard Atlas mechanism into a Bachmann RS-3. It took only a few cuts to the shell, which the cab covered anyway, and no need to mess with frame milling. The loco still runs great, although it’s a 251 engine sound instead of a 244. But this was done back when even LokSound couldn’t fit in a narrow-hood diesel without removing most of the weight, so I was happy.
-Steven