Of course, the extra gig of RAM won't help until you actually
use more than a gig of RAM. Until then, it just sits there.
Your RAM clock will not limit your CPU clock with a Venice. The RAM and memory controller have their own bus and so are always in synch. Hence, there is absolutely no latency penalty for using a memory frequency divider. In fact, even at "1:1" you're actually using a divider with the A64. So you can have the best of both worlds. OC the CPU to 2.7 or whatever it will do, and use a divider to keep your RAM happy. You'll loose only a few percent in real world performance compared to 2x512MB, and when you run games that use more than a gig, the 2GB setup will be
much smoother than 1GB+pagefile.
You might find this thread helpful:
http://forums.anandtech.com/messageview.aspx?catid=28&threadid=1475190&enterthread=y