I use one of a variety of solutions to put the low end of a mix into mono, or more specifically, narrow its representation in the stereo field. Izotope's Ozone5 has a multiband stereo imaging section that allows negative values to narrow stereo perception. I'll set that to a low frequency range and really hit it hard with negative values. Works great. Airwindows ToVinyl does a great job of this as well, but is only available in AU format.
...I'm getting pretty far off topic here...
FS: DBX 286A Channel Strip (FS thread coming soon!)