When I started writing on the forums back in April 2009 there was much talk about this topic. You might want to check back to that time if you find you want more on this.
I echo what others have said on here but wanted to add my own opinion that, like everything else with poly, take your time, talk about boundaries and don't have expectations, always ask first until it comes naturally.
When it feels right to everyone, it is right. It sounds like you have some distance to go with the two men you are interested in first. Take the time to do it all right and it will be so natural and worth every moment of work you put in as far as I am concerned.
Enjoy and good luck.