Well it would absolutely depend on your setup, if you have a small cab or box and plan to use CFL's you might be able to get away with it, however if you plan to use MH/HPS then your probably going to need at least a 4" inline like the one Metasynth linked to, although the best deals Ive ever seen were on Craigslist, most often there used but in good working condition. Post some pics and info about your setup so we can better help you.