Similar to what Mike was recommending, one issue seldom mentioned is stylus tip size. That may come down to the mono records you intend to play. Are they original monos from the '50s and early '60s, or reissues produced within the past 20 years?
Early monos were cut with a larger tip, 0.7 to 1.0 mil for LPs. Nearly all mono reissues were made with stereo cutter heads with smaller size. I don't believe few if any mono cutter heads survive.
I assume from this mono reissues may be OK with current stereo cartridges, although a mono switch (per Lew) may still help sonics. But with original mono releases a mono cartridge with appropriate tip size should optimize the enjoyment.