Still waiting for my roadname to come in, so I can't give many specific details, but something very important to understand about sound units: They won't run at anywhere near the same speed as non-sound units on a DC layout. Sound units draw a lot more power and need somewhere around 6-8 volts to start moving, whereas your other units will have taken off long before then.
Go here for my rail shots! http://www.railpictures.net/showphotos.php?userid=9296
Building the CPR Kootenay division in N scale, blog here: http://kootenaymodelrailway.wordpress.com/
looking for your opinion on the latest run the sd40-2 locomotive as to how they run on a non dcc layout with a kato or atlas engine when hooked togeather are they worth the money