Opera in Prague?

[rubio]

I'm going to Prague 7-11 of May. I have already booked Mahler 2 with the Czech PO, and now I wonder if I should try to see an opera as well. How is the quality of the opera nowadays in Prague? I see the most famous places are the Prague National Theatre and the Prague State Opera. When we are visiting I see Dvorak's Rusalka and Verdi's Nabucco are on. I haven't heard either of them. Would you recommend to go, and what do you think of these two works?