To set up another set-up for mono could give you better replay, but you have to consider weather or not you choose to make the expenditure to put your system at the forefront of superior playback capabilities. A mono cartridge would have to be of superior quality to be able to gain benifit to your stereo cartridge of superior quality. Most would spend as much as they can on the one cartridge because the better stereo cartridge more often gives better results that splitting that budget in two, then there is the expence of another turntable of quality, and the arm, or getting an arm with extra armwands. You didn't mention your arm or cartridge, or your spare table that perhaps somebody could be more specific. I have had no experience with mono cartridges, but benz and lyra are both offerring high end mono cartridges, and there must be something to that.
Of coarse, if you were to set up a mono set up of quality, and used different components than your stereo set up, it might just sound different.
I often use the mono switch to good results. It doesn't really make to much difference on mono recordings, but on those that are reprocessed for stereo, the results sometimes amaze me, and please me.
The generalization that I understand is that it is not really cost effective to double (or increase) a budget for mono playback, but I am also interested in expriences others have had with this.
I think it would be real fun to optimize another set up for mono. Can't have too many turntables, right?