DJM-700 Mixer

Guys a question in regards to my DJM-700.

At present at home I'm using RCA cables to connect to my home amp/stereo via MASTER 2 and the  MASTER ATT. is set at -3db.  I am a upcoming first gig at a venue, I assume I will be using their XLR speaker cables into my mixer MASTER. 

Should I adjust the MASTER ATT. at a venue?  Not entirely sure why it's set at -3db as I don't recall moving this if the default is 0db.  

If I do use monitors i'll connect these via the BOOTH RCA - although unsure if I'll do this, may rely on the venue speakers and my headphones as the venue is rather small holding around 300 people.

Thanks,

Johnno