Thanks for all the replies folks. I realize that a certain amount of 'grain' is intended with Acros, but it just seems to me to get a little out of hand as soon as ISO gets beyond maybe 800. For what it's worth, I had a quick play with the X-Pro 2 again last night and the other simulations are certainly cleaner. Maybe I was just expecting a little too much from Acros. I'm not currently able to get in front of the PC I use for editing, but will post some pics in the next few days as examples. As for Silver Efex, I've always liked what people can achieve with it. Unfortunately though, my preferred software is ACDSee Pro, which doesn't support Siver Efex.
Again, thanks for the replies. Much appreciated.