I would initially stick with the stock Rega Carbon cart. I def. would not want to move into the direction of warmer.
How would you specifically compare the Nagaoka to the Orotfon Blue? The Blue seems to have a lot of fans.
The Nagaoka's are warmer, smoother with deeper bass. They are more forgiving of surface noise. I have heard the 2M Red on my TT and I have heard a friends 2M Red and 2M Blue. Both ortofons sound similar with the Blue being a bit more refined and more clear sounding. Both are brighter sounding than the Nagaoka's. Their top end has too much treble energy for me. I am not a fan of the 2M Red. I find it very fatiguing. I would not pair the ortofons with a phono preamp that leans to the brighter side.
The Nag's are not overly warm or syrupy. They do have a deeper and very musical midrange. They need 30 hours of break in otherwise the treble can sound a bit rough. After 25-30 hours the sound really smooths out and they sound great.
Here are some reviews by a guy comparing several cartridges in different price groups-https://www.youtube.com/watch?v=9U5ANqGccmkhttps://www.youtube.com/watch?v=ZhSFP0PJCE4https://www.youtube.com/watch?v=eyosUmVSzxg&t=17shttps://www.youtube.com/watch?v=ZBAOSJrkde4
The top 2 reviews on on the MP-110 and MP-150
The bottom 2 are the 2M Blue and Red. The reviewer preferred the MP-110 to the 2M Blue and other cartridges that cost twice as much. Of course as usual, it is so subjective and system dependent. However, my experience with all 4 cart's mirrors the reviewers.