If you are in the states, Amiga on the Lake is a great site for New Generation Amigas as well as some classic stuff sprinkled in.
I have dealt with them for some time and they are very good to work with. I think right now the X5000 full system is available as well as the mainboard only option if you want to build it yourself.
They will also be offering the Tabor if that ever actually sees the light of day.