I have heard nothing about the Aopen board, but I know the Abit NF7 is an excellent Board, one of the best AMD boards money can buy - especially if you're overclocking.. the most reccomended nforce2 boards are:
Epox 8RDA+ - cheaper than others, plus good for OC (lacks SATA)
Abit NF7-S - lots of features excellent OCers board
Asus A7N8X Deluxe - LOADS of features (e.g. 2 LAN ports) reasonable for ocing, but a little expensive..
So out of your two choices, I'd recommend the Abit board, simply because it's a known performer. I'd consider the AOpen board only if there was a substantial price difference.
If you don't intend on using SATA, I'd reccomend the Epox board myself, as it'll save $15 or so.
<font color=red>The preceding text is assembled from information stored in an unreliable organic storage medium. As such it may be innacurate, incomplete, or completely wrong</font color=red> :wink: