Syphus, thanks for the fascinating adventure. I focused on US and French accents early on, then developed a focus on Chinese accents. I hardly bother with the rest.

http://www.languagehat.com/archives/003883.php

Although Russia has some accent variation in location, it's mostly a Slavic language that differs in accent for each Slavic country. That said, in regards to plays like Chekhov, the emphasis is not on accent. So, for actors, you are right. The emphasis in Russian will be on the vocabulary and syntax. The accents will be the same. Amazing!

BUT it does say Moscow has a bit of it's own accent. Something to consider.