ANY engine with only one truck powered, is a P*** Poor example of pulling power). You therefore could get a jaundiced view of what model railroading should be.
In HO, an InterMountain ‘F’ unit is an all-wheel drive and pickup that is totally a different ‘animal’ than what you descibe. An IM 'Smart Dummy (or B with motor & gears removed) can easily be hauled by one or two powered units - probably one.
It probably would be simpler to use all motored sound units, however 5 diesel head-end power is decided overkill, and definitely uneeded… It also looks funny on most layouts. Buy a single IM ‘A’ unit and go from there.
unless the B unit is a powerless drone (stealing power from the A unit), techniclly having sound in the B unit is correct, and adds to the effect, depends how far you wanna go.
If you guys have the money to toss around for an all-powered, all-speaker ABBA combination, “more power” to ya’. However, to get the best sound: the more unobstructed space you have inside the shell; the better your sound will be. So, speakers crammed inside a motorized unit just aren’t necessarily going to sound as good as those properly positioned inside a dummy unit.
I have several A-B-A lash-ups(consists) on my layout. They are connected with drawbars. They are also connected with wires. They could be programmed as one locomotive or three locomotives. Running out of slots on your command station is sometimes easy with several lash-ups and some DCC systems. I started before BLI, Athearn and others came out with factory installed sound. I also now have a couple of lash-ups that have sound in all units.
The lash-ups with two “big” speakers in the B unit have fuller sound, (the frame has been cut out where the motor is usually mounted in the B unit , so a big sheet lead enclosure fits and fires down. The sets with all three sound equipped engines in the lash-up sound great with the three air pumps, engines etc opperating out of sync with each other is really cool to (but they are weak in the bass). That being said It is more expensive to have three sound equipped engines and three seperate engines do take more slots in my Digitrax Empire Builder DCC; however, they could also have same address to save on slots.
I use a Soundtraxx DSX decoder in the B unit. Factory installed sound is much less work also. I have one set that is a FTA-FTB by Stewart with a Athearn Genissis Drive & a Highliners F2A. (that is why the NYC bought the F2A) I have digitrax decoders in the two A units. They look, sound and run great You can customize the speed curves so any different engines run MUd with no problem. I have a BLI F7A-B-A set and they look and sound great also.