with the Song towers I would run a sub more like 45Hz and below... perhaps 50Hz, or 60Hz if it is more convenient, or 60Hz if your sub will allow it. This is based on response ratings only. (80Hz seems to be a default setting for most systems) I think the STs actually reach into the upper 30's. I am sure that SongTower owners could offer better advice concerning crossover point than I can, but based on what I can extrapolate a crossover setting of 45Hz would be about as low as you would want to go.
Also sorry to hear about the layoff, I feel your pain.
-Funk