The Lepai is not really helping you here. With only $100 for speakers and wanting bass, I think you should skip the amp and get a 2.1 media speaker system is the best solution.
The THX certified Logitech 2.1 systems I have heard sounded pretty good for their price, and a 7" sub is as good as you can reasonably ask for:
http://www.amazon.com/Logitech-980-000402-Speaker-System-Black/dp/B003VAHYTG/ref=pd_sim_sbs_147_3?ie=UTF8&refRID=1V8AR9CCTBM95JKTQY9Q
If you don't want to go with a 2.1 system, I agree on the Mackies.
It is simply the way of things that pro-audio offers better value. I don't believe you will find as good of a speaker with out the amp.
Of course, finding the right deal on Craigslist will trump all other options.
If you tell us where you are, we can check your Craigslist for deals. Of course it is up to you to check the condition of the speakers.