We have a club member with both Kato and Fox Valley with sound, but the speakers in N scale are so tiny you can't really hear it unless you are in a very quiet environment and the locomotive is within a few feet.
Speakers that will fit into N scale are just too small to ever sound good.
99% of all Decoders are universal between brands of DCC systems.
Some decoders are better than others. In my opinion, MRC does not have a good reputation for decoders. I have an NCE system at home and use Digitrax at our club, but I perfer TCS decoders for N scale and Soundtraxx decoders for HO scale. I just think they are better and easier to set up and program than other brands.
You can get N scale size decoders that have sound, but you have to remove a chunk of weight to have a place for the speaker in diesel locos. If you are going to run steam, the speaker and decoder will usually fit in the tender.
As for having the lights off on the second and third units in a consist, it depends on how the locos or decoders in those locos are programmed. Most decoders will allow you to do that. You just have to find the right CV's, which will take some research in the manuals. Most decoders come with a simple start-up sheet only. You will have to download the comprehesive manuals from the manufacturers web site.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
Jimmyboy0727,
Seeing as how you are new to DCC, this site has a lot of info, for you to read up on. I should have it already set for: DCC for Beginners. IF it is not already there then click on it and read away.
http://www.wiringfordcc.com/intro2dcc.htm
You are always welcome to ask any questions on the Forums, there are many here that will gladly help you.
Frank
I've never used it before but want to now. I will be running n scale kato and fox valley Bnsf Gevos, kato metra and amtrak units. What decoder has the best rating and do they come with sound? Are these decoders universal between brands if I use a digitrax system? I heard that the decoders can be programed to have the second and third units lights off while behind the lead unit? Any help is appreciated.