This should fit in your budget, based on your choices:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131792
The ASUS board has a longer warranty and is probably a much more solid board that the AsRock.
The Asrock has a 12 power phase design, while the ASUS I believe has a 16 power phase design.
Power phase-correct me if I am wrong- can influence how high and stable you can overclock.
Really, anything about 8 shouldn't make a difference.
The AsRock seems to be the best bang for your buck though.
You can't go wrong with either one, but if you just want to save some extra cash, the AsRock should meet your needs.