If you don't run a subsonic filter, you can really only run about 600 befroe you need to worry about reaching their excursion limit. The 150WRMS recommended is because of the excursino below tuning that these sub exhibit and the high tuning that they want. 34-35 hz is actually well below optimum for what those subs want and because they movea lot of air, you will need a big and thus really long port to keep port noise down. If you really want to tune them that low, you would probably be better off with a bigger box.