The unit is h10025.www1.hp.com/ewfrf/wc/document?docname=c01481519&cc=us&dlc=en&lc=en
It currently has h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&docname=c01489642
The TouchSmart IQ504 was also released with h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&docname=c01635715

Some concerns I have with upgrading the motherboard beyond either of those 2 stock options are:
-the motherboard, CPU, RAM & etc fitting in the unit.
-and the ports lining up around the unit

Suggestions? :D