About the ASUS motherboard we had this thread going, where I found another person that was having trouble with a large amount of RAM on that board. Does not mean all DIMMs are affected but I could not make it work at least.
I went with the GIGABYTE MC62-G40 because I got my hands on that the easiest as a replacement but I would maybe more closely suggest the ASRock WRX80 Creator R2.0 because I think it is better suited as a workstation board. I needed an Intel network card though and the ASRock does not have that.