It will be hard to fill that room with deep extended bass for less than about $750. You can do okay for about $500 with SPL, just not good extension to the lowest octaves. Even with $750 it's not going to be super extended, but it would be better.
You can get a respectable receiver for about $250 delivered in the
Onkyo TX-SR505.
That would leave you $500 for a set of speakers. Most likely you'd just have to look around for a used setup.