Meta on ul. Foksal is even better thank Przekąski/Zakąski, imho
That's one of my haunts too. It's best late at night.
For another couple of late nght ones, I'd add Bar Warszawa (like Meta but bigger) at the bottom end of Miodowa and maybe Drink Bar on Wspolna.
details on the complex at Fort Mokotow.
It isn't an organised complex, but the address is ul. Raclawicka. The only bars on Raclawicka are there.