Hey there...
I want to recomend the after office party that takes place every wednesday at the"Museum" club (Peru 500, Capital Federal BA).
It kicks off around 19hs but the best time to get there is aroung 22hs. All the locals go there dressed in toxidos (like all of them really come from the office jaja...) and all that...
The music is great, the girls are amazing and it's a great party in the middle of the week.
I recomend dressing well to avoid problems at the entrance.
Have fun...

P.S the party ends around 3 am. You can continue to one of the after parties you'll hear about there.