I've had a paper in a peer reviewed journal and, technically, a poster presentation at an International. It was my MSc dissertation both times.
I can't really advise on whether you should dedicate yourself to your PhD or submit to the conference. What year are you in? I would however advise that before you start work on it you check who, if anyone will fund your conference. My poster was actually presented by the second author in the end because no-one would pay for me to go (boo, hiss!).
The paper, I started with the best relevant journal that we stood any chance of getting it in and, fortunately for me, they accepted (after I jumped through numerous hoops). If not I would've started working down the list of relevant journals in order of their IF rating.
Good luck!