Don't trip over our crappy submersibles...
Yeah, Russia's Military Behemoth really impressed me to death recently when they called the British (and us) in to free their mini sub. RELAX people. They are a regional power at best.
China at this point is a totally different animal than Russia. Bill Gertz talks a lot about what China is doing.
Notably, China is a Communist country (supposedly) that does have a strong economy, and does spend money on weapons (at least according to Gertz).
Yes, this is all of serious interest. What's of much greater concern (in my opinion) is the transfer of nuclear material and know-how to countries such as Iran.