Yeah, should be fine. If possible, arrange them so that the FX5200 is the primary card, and the MX400 is the secondary card. When it comes to gaming, if any, you'll use the more powerful of the two cards.
If you're ever in the market for a new card to upgrade both of those, let us know. There are much faster single solution cards out there in AGP trim that can do everything you're asking from one card.