cnrising wrote:
Any recommendation on the sub? I know EZ has sub that can pair with my EZ speakers, but cost is about 600 for one.. I can try to squeeze this in, but will be this overkill? My basement is about 30x20.
Overkill is subjective - my home system consists of 2 15" cabs & 2 18" subs - approx. 3400 watt (max).  Depends on what you really are expecting. 
You only got a single cabinet right now correct?  I'd go for another cabinet before getting a sub - may be all you'll need.