The UD7 only has 1 PCI-e x1 (which will be used by the xonar) and one PCI, so as long as the wireless card is a PCI card your good to go![]()
A wireless card or the sound card would work in one of the x16 PCI-E slots.
You can use a x1 card in a x16 slot though you would have to check the effect on the speed of the other x16 slots.