There have been a few kitchenPC threads using the itx form factor. I haven't seen a bar one, but I don't see why not.
YOu could just buy a new car system and put the old car system by the bar.
Someone made a recipie plugin for RoadRunner so you could store all your drink mixes and such on it.
As far as Xenarc goes, they are still around and kickin'. Lilliiputs just seem to dominate because they are cheaper. Xenarcs are still there though. In the store, on eBay, everywhere!