Unfortunately, the Kobo's don't have a Russian dictionary. But, there is a way to add one.
PDF is mixed blessing. The display is very good, but can be slow. But the navigation isn't great. And they don't do PDF reflow. Personally I avoid them, but a solution a lot of people like is to install Koreader.
Other than that, any of the Kobo's will fit your requirements. And, at the moment,
JB HiFi have the Glo HD at $159.