Hi Rico.
I've just built a new i5 DAW using a low end ASUS P8B75-M motherboard. I read somewhere that this board still uses a 'native' pci slot for compatibility with legacy devices. Most new boards seem to use PCI emulation which is not OK for PCI audio interfaces if I understand correctly.
Though I don't have a Layla24, my Layla 3G is absolutely smooth with this board and 16GB RAM. Sonar X1 is happy with the Intel onboard graphics as well. I haven't been able to get X2 to run as well as X1, but looking at the forum I think that is a problem with X2 and not the motherboard or Layla 3G.
The P8B75-M is still widely available AFAIK.
Cheers,
Phil.