I personally do not know of an undergrad who got his/her work published in the top 5 journals. However, it is a possibility. The best strategy in my opinion is to show your work to your recommenders and ask them if you should send a copy of your work along with your application. As far as getting published goes, it is perhaps better to wait it out than to get published in a lower level journal since it would be a permanent entry in your cv. Econphd.net offers much the same advice, and I find it quite plausible that Econ. departments may want a clean slate. If, however, you feel that your work is of top quality and you don't mind spending on submission fees then do send in your work to the top places. If it gets accepted you're guaranteed some good offers, if not, the editorial review may offer you some tips on future work. Overall, I don't think getting published at a lower ranked journal, is what you should be worrying about now. All the best.