Well, not all guys would like for you to go straight forward with that. SO I would suggest slowly easing it onto him by brining up questions like/ " What kind of house would you like to live in" " Would you move in with me if you had the chance" And questions of that nature.
That would honestly be the best way to ease it onto him, not by simply brining it up out of the blue.
Go for a drive with him and drive by the house. Then say something like, "Oh, I like that one! We should go look!" If he questions it, point at something in the yard (You'll have to put it up) that says, "Come on in!" or something like that. Have all of the moving stuff already there so when you go in and he asks why its all there, tell him casually, "Oh, because this is our house. We have a lot of work to do and we're burning daylight, let's get to it!"
Not my best idea, but I can't beat iNaZzy's idea. :)
Organize a little treasure hunt. Start at his/your old residence with a clue to find an object (household items for example), that item then holds a clue to the next item and so on. The last item should be inside the mailbox in front of the new house and it should be a key with a note: Welcome home