MP150 or MP200


I am currently using a Nagaoka MP110 cartridge and want to upgrade . I really like the Nagaoka sound and was considering staying with the Nagaoka sound . My question is will I get a considerable upgrade in sound going to the next level cartridge which would be the MP150 which would be a 329.00 investment or in order to get that big upgrade I would have to go to the MP200 which would put me almost at the 500.00 mark .
mcmvmx
Project 1 expression2 with modifications and speed control . elekit tube preamp upgraded and modified using Jan 12AT7 with SS phono stage connected to Mccormack DNA125 amp 
 All interconnects , speaker cable and and power cable are JPS Labs superconductor connected to Richard Gray power station . Speaker are Magnepan MG12 with external upgraded crossovers . Digital duties are carried by a Opera Audio Turandot CD Player 

You can change the stylus, not a cartridge
Get better nagaoka stylus
My system sounds ok . There is a video on youtube where they swap the stylus and it doesn"t seem to make much of a difference . Nagaoka states that in it of its cartridges the generator system is updated like better windings , purer metal and it seems that the cantilever assembly has been tuned for its particular generator . That would mean that one particular stylus and cantilever assembly will sound great with the cartridge its intended to but will degrade the sound if you changed it to another cartridge in its lineup . Another problem with Nagaoka is their pricing strategy.
 They went up in price some time ago and are expensive . I have the MP110 which cost me 132.00 . If I which to buy the next up in line , the MP150 I would have to shell out over 350.00 ! And the next one up would be the MP200 at almost 500.00 . And then there is the 300 and 500 which is 1grand !
You MP110 is entry level model with bonded elliptical diamond and aluminum cantilever.

Higher model like MP200 comes with NUDE (not bonded) diamond and Boron cantilever. One of the reason the price is much higher. 

Never use youtube as reference in cartridge comparison tests. 

As you said you want to stay with Nagaoka, so you could investigate which compatible stylus you could buy instead of a new cartridge. If you have cash for MP200 go for it. 

In my opinion you can easily find a better high compliance MM cartridge like SONY XL50 with Boron Pipe cantilever, but you want to stay with Nagaoka. 

$500-700 for a great MM cartridge is fair price.