Most consumer boards do not support the Xeon CPUs, as they are geared towards high end workstations and servers. Quickly looking at what Asus offers, none of their Z68 seem to support the Xeons, at least according to the CPU compatibility lists, but one of their P67 models does. You can look at the specs here. Looking at newegg this board is quite expensive, $245. Integrated graphics would also not work with this board so you would have to get a graphics card.
I would say if you can't afford the i7, you're probably best off getting the i5 on z68. The only boards that support the Xeons are geared more towards workstation use, and they are consequently quite expensive. If you can't afford an i7, I doubt you can afford to drop more than $200 on a motherboard. You can try to use the Xeon on a board that does not list it as a supported CPU, but there is no guarantee that the CPU would work properly with that board.