Go with the subwoofer approach. If you love your monitors and want more bottom end definetion and full range sound, doing a pair of subs like the Vandy 2wq's or Revel B15's is the way to go. The Revel B15 is probably the absolute best musical subwoofer on the market(and also the absolute most flexible too as it has unlimited room contour ability along with every input/output you would ever need) at ANY price, the Vandy is great for half the price.
