I really recommend Nik's place, it is a well located apartment that makes it very convenient to explore the best of Athens.
It is a bargain, the communication is very easy and convenient, Nik and his brother, Mario gave me all attention I needed and even waited for me for a check in in person when I was stuck in traffic late for the check in appointment.
There are plenty of night life options nearby, the subway, tram and bus station are very close and convenient.
You can go to Acropolis walking without a problem.