Alright to start off, you can use any brand decoder with any other brand dcc system. NCE, TCS, MRC, Lenz, Digitrax decoders are usable with any of the dcc systems out there, thats part of the NMRA specs.
Secondly, theres only 2 decoders thats Athearn Blue Box ready, as far as not having to solder anything, and thats the Digitrax DH163AT and the Digitrax DH123AT.
http://www.digitrax.com/prd_mobdec_dh163at.php
They have the connectors that fit on the motor connections and fit onto the pickups for power.
But, I think you would be better off doing the wiring yourself. Its not that hard, and after 2 installs, you'll wonder why you didn't think it was easy.
Those 2 decoders cost more just because of the wiring, and then they dont have good connections because they aren't soldered to the motor or pickups.
Once you crack that shell and start playing with wiring up ditch lights and then sound, you won't regret it.
Just take your time and you'll get it right. Its as simple as removing the athearn motor from the chassis, break the 2 little tabs off the bottom clip that pickup power from the chassis. Put a small piece of tape across that area. Solder the grey wire from the decoder to the bottom clip of the motor. Re-insert the motor into the chassis. Solder the orange wire to the top of the mototr clip. Solder the red wire to the engineers side of the chassis pickups (normally the 2 L shaped stands on the trucks, that the top of the motor and light get power from by way of the long multi-bent strip on top) and then solder the black wire to the area just in front of the light bulb on the L shaped metal that attatches to the chassis. Theres all you need to power the motor right there.
As for lighting, wire up the white wire to the back of the factory bulb and thats done. Any other lighting and you'll have to install the bulbs for them.
As for which dcc system to get, hmm, thats a very debated subject on any forum.
1st, are you gonna join a club? If so, then get a system that they are using.
2nd, if not then you have a whole lotta options avail to you. Try to find a local hobby shop and try out what they have and see what you like. If you have any friends that have dcc already, ask to use theirs on their layout. Try to go to any train shows that may be coming near you and observe their use of the dcc systems.
I cant recommend a system to you as I dont know what you need it for, how many locos running at 1 time, how many of them have sound, how large is your layout, do you intend to expand the layout, how many people do you expect to have running at one time, how much your willing to spend right off the top, will you be needing boosters for other districts, and so forth.
Give us an idea of what you need to do and then we can give you recommendations of what system you need.
