Hi Paul,
Yes these units are great, I've got them in most of my locos, and have fitted them to a number of decoders with SUSI interfaces including the eMotion L. It is a cheapish way of adding sound with no loss of quality.
As has already been said the Uhlenbrock IntelliSound - Module 32300 is the a rebadged Dietz micro-X3 and Chris and A & H Model (http://www.aandh-models.co.uk/) is a good supplier.
Use the usual Massoth speakers for LGB locos.
Sounds are available for almost all LGB locos and many others. To see what is available go to the Dietz site (http://www.d-i-e-t-z.de/) click on 'download' then 'sounds'. Any of the DS3 or DSD sounds can be used. Also it is possible to hear the sounds by clicking on the 'sounds/Lieferliste' link.
For an English manual go the the Uhlenbrock site (https://www.uhlenbrock.de) click on 'download' then 'Handbucher' then 'English' the 32300.
If I can help in any way do let me know.
These are easy to fit just two wires to the speaker, and plug into the SUSI. It is possible to use a hall sensor but I haven't bothered with that.
Dietz will soon be coming out with the micro-IS4 which is an improved version of the micro-x3. The claimed improvements are:
more power via a digital amplifier, works on analogue (if supported by the decoder), more configurable, own sound programming.
Uhlenbrock will be selling this as an Intellisound 4 module.
As Jon said there have been price cuts on the micro-X3, presumably trying to get rid of them before the new version comes in.