Here is a website that is here in the UK that supplied the older board Francine has and also lists a replacement for it.
http://www.digitrains.co.uk/ec...-eco-400-diesel.aspx
The description of the board is a bit misleading and they could have made it a bit more clear.
If you look at the spec information, it is the audio bit on the left hand side that is the bit that tells us what you need for speaker requirements and a bit further down it actually gives a couple of examples to choose from.