Thank you all for the response.
So 500 for a. 6 day stay would be enough to live but you wouldnt have much fun. I think double it and you will be ok.
I think I can manage close to 1000 USD. Personally speaking, attending the conference is top most priority for me and if budget is tight I wouldn't mind spending time in my hotel room rather than sight seeing or enjoying local food.
My main concern is whether will this money be sufficient to satisfy the visa officer that I will be able to survive my stay in Poland ? I will be able to provide documentations from the conference about them paying my travel and accommodation.