Following DFI's footsteps.
I got the juniours, and got 4 Ghz down on a Phenom 1 on 790GX M2RS (LP JR) and 5 ghz on PHII.
Tried the P45 for abit on water, did 4.7 on a 8600.
Respectable results, i do not know much about asus, but i know atleast juniour motherboards can be about as good as the big ATX boards.
There is one downside on the dfi boards, you get more EMI from stuff, due to size, and stuff is closer together, this is mostly hearable when you clock much, running stock on all, run spread thingy, and its almost gone.
Thats my experience on M-Atx, got a m-atx box at home, and its ACE!
Waiting to see more m-atx boxes, i know this is what we will only buy in future, when SSD get more popular