Jostenmeat,
We'll be in this apartment until approx. October 2012. This coming November is our wedding in Sanibel, FL and we'll use the 11 months remaining on our lease after that to search for a house.
I've actually already been doing what you recommend, which is routing the LFE information through the Mirage towers I'm using as mains right now. It works well but there is a problem: when listening at moderate-loud volume, the very very low effects (sub-30Hz) cause the woofers to unload and bottom out. The towers are a ported design that I believe is tuned to ~40Hz so this is not terribly surprising. They are bi-amped as well, and so are receiving healthy power from my Yammy AVR.
So, in the interest of not setting my front channels on fire, I'm leaning towards a discrete sub