I think he meant lower latency memory. Lower latency memory will help, although I'm skeptical of how much of an actual improvement you'd see. I will say that the difference between "bargain" RAM and lower latency RAM is noticable.
Higher clock rates will DEFINITELY help. This seems like a silly thing to mention these days, but dual channel memory will make a world of difference to. Personally I'd sacrifice quantity for speed - if you're not running the fastest RAM your setup will handle, upgrade to what the setup can handle rather than adding more memory. Get the fastest RAM (clock) that you can get and something with reasonably low latency. Just my opinion though, do what's right for you man!