Unless your amplifier already has an in built phono stage, you MUST get a phono preamp in order to be able to listen to anything off a phono cartridge, regardless of whether it is MM or MC.
So it is not a matter of whether it improves the sound, it is essential. The reason is because while almost all other audio sources generate signals which are appropriate for an amplifier to handle, a phono cartridge’s output signal is very much lower and hence needs a lot more amplification.
In addition, the phone amplifier provides something called RIAA equalization without which, the sound would be awful, which only phono preamplifiers provide.
Furthermore, the output signals of an MM and MC are very different. MC signals are even less than MM signals by an order of magnitude. So, ideally, the phono amplifier you must buy should be able to handle both types.
Luckily, in today’s marketplace, there are literally hundreds of very good different types of phono preamplifiers, ranging in price from $100 to more than $45,000. Your choice depends on your budget.
Some that I recommend are the wonderful Schiit Mani (its price does not do it justice) at about $150, Rega Aria at about $1500 and at the absolute ridiculous top end, Pass Labs phono preamp at $45,000.