Playing mono records properly without breaking the bank - a phono pre-amp question.

Audio-Technica VM610MONO Phono Cartridge Grado ME+ Mono Cartridge Ortofon 2M Mono Phono CartridgeParasound Zphono XRM3 good mono cartridges that won't break the bank and a phono preamp with a a stereo/mono switch
phono pre for $599.00 and 3 cartridges from $125.00 to $375.00

Folkfreak and Lubachl, The better experiment, to work around Folkfreak's valid point that when comparing stereo cartridge A to mono cartridge B, you have to guess at the differences due solely to the basic goodness of the two cartridges, is to compare, for this example, your expensive MC cartridge in stereo mode to the very same cartridge with the mono switch engaged.  This is what I do all the time, and I cannot think of an example where I liked the stereo mode better than the mono mode, using a preamp with a mono switch to amplify the signal from a mono LP.  (Of course, I am only talking about "modern" mono LPs, not 78s, which are not LPs at all by definition, or late 1940s/early 50s oddball recordings.)

Elliott, have you used the KAB mono switch? Looks like an interesting solution, although another device in the chain could result in some distortion.

Thanks everyone for chiming in. Personal experience is always helpful from others specially at different price points. What I'm gathering from the comments are:

a) best to have the "mono switch" within the phono preamp to minimize any added signal loss and/or distortion.  I'm planning on getting a used phono stage so the KAB mono at $200 feels money best spent on a phono with mono switch. And don't see any KAB mono in the used market.  Thanks elliottbnewcombjr  for the suggestion.

b)Stereo cart may sound as good /better than a Mono cart, but as anything in this hobby feels like it depends on the implementation of the product, cost difference, etc. The example of the  $1k mono cart having more soul than a higher priced stereo cart certainly shows that there is room for experimentation once/if one goes deeper into this hobby.

c)Not being able to have a mono cart, separate rig, separate tone-arm, but having a mono switch may buy some time before the upgrade-itis kicks in.
As a picky perfection seeking engineer, looking for the highest resolution and imaging in my current digital rig, I'm sensing that I won't sleep soundly without a mono switch on my future phono preamp.

Just use a good stereo cartridge with good channel separation. 

Lots of garbage being spewed out trying to sound knowledgeable or scientific. 

You dont need to disable the stereo cart. The ever-so-slight differences in channels will be cancelled or helps to add depth to the playback. Disabling causes a very lifeless, dead, flat quality to playback. Save yourself the trouble and expense.