Buy or trade RS boards/chips?

Contact Boxcar Bill here in the forum and he'll get you a discount on the ERR products.

Ypu can get an Alco sound board from Boxcar Bill at a discount.  I have 2 Alco C420s I upgraded that have the board and I like it a lot.  It is the one listed as RS4Alco by ERR.  I liked the sounds so much now I have 3.

You "may" be able to just buy the two chips, I did that at one point, don't know if that option is still available.  I think you can get the sounds that are available on the ERR website for the RailSounds Commander.  As I recall, the price was around $30.

Flash-my 2 Alco C420s were the 'command upgradeable' versions from Lionel.  They actually need a different board than other Alco versions, but the sound is the same.  I'm not sure what your Atlas RSD4 would need as far as other boards, but I can vouch for the ERR Alco RS sounds in the end.

I'm kind of sheepish to admit this, but I will share this insight.  I just bought back another Lionel Lehigh Valley Alco C420 that I had traded away.  It has a whole different Alco sound board that is really distinctive.  I missed the darn thing and made a deal to get her back.  The gray and yellow version.  You can't buy the sound board for this locomotive seperately.  The same is true for all boards that are engine specific.  You have to send the original back to Lionel to get a matching board.  Of course this board will have crewtalk with the engine # called out, whereas a generic board can't have that.