Asrock aren't exactly renowned for their overclocking prowess, and the only stuff of theirs I've seen has been pretty middle-of-the-road stuff - Alright for putting together a cheap system, but if you're interested in overclocking then I would avoid I think, but I haven't seen any reviews or anything about their A64 boards.
Asus tend to make feature-rich boards, but they tend to have voltage regulation issues (or at least they have done for a while, someone please correct me if this is no longer the case) which limits their appeal to the overclocker. No problem for stock speeds or mild overclocking though.
The MSI is well-liked I think. I've not used one myself, but it has lots of features and apparently overclocks quite well.
I have a Epox 9NDA3J myself. Great board, seems a good overclocker (got 250x10 at the moment, 260x10 is pretty much stable but I think I need either more CPU VCore or slacker RAM timings.... but this is not the time to go into that!)
From your list, I would get either the Epox or MSI, personally probably Epox as I've had good experience with 'em.
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