Crap, before I even posted my brilliant life saving reply, they done changed the software already...
Was going to recommend a freebie mono convolution unit, Reverberate LE.
Now even the teaser is stereo:
http://www.liquidsonics.com/software_reverberate_le.htm Really good program. So many impulse files for free on the internet. Even if stereo capable, if you load a mono impulse, result is mono. CPU load differential is not significant.
What I really like about convolution reverbs is that you can open the impulse wav file in an editor. Audition, Goldwave, whatever. Screw reality of some European church setting. Warp and bend the wave form. Time shift, flange, eq the yin yang out of it. Save and reload. Way more interesting than sitting in some heathen church listening to the choir bounce off the walls.
Also, multiple audio editors allow wav file downgrade from stereo to mono if that is what is required. Stereo to mono the file, and reload in a convolution plug.
John