I second (third?, fourth?) the recommendation to get a sub. I would urge you to do something though. Call both Axiom and SVS and have the conversation about the size of your room, what openings you have, tile/carpeting/hardwood floors, etc. They are both wonderful to deal with and will get you to a level of detail to make the right choice.

BTW - the 2805 is more than ample enough to power the speakers/sub.