Surely the important point is that you love the sound you have currently. The only way you will know what you are missing (if anything) is by auditioning some new amps for yourself.
I am no expert in this area but if you are not hearing any difference then stick with the less expensive option. What your ears are hearing is all that matters.
Is the tracking weight on the turntable set correctly. Maybe adjust it a bit to see if that helps with your records. My experience is that this can have a big impact.
CD Player with FM, DAB and DAB+ Digital Radio | Bluetooth CD Stereo System with Remote, Aux, USB Input and LED Display | Majority Oakington | Compact Hi-Fi with Adjustable Bass and Equalizer | Walnut https://amzn.eu/d/7WIt81Z
something like this maybe?
If you are happy with your current set up then I would go with the 2M blue stylus and then buy some more records. Easiest option and I am pretty sure you will notice the difference. If you are not happy then maybe a different flavour of cart is the way to go.
I don’t think the Oberon 5 will give you what you want. The Zensor 3 are pretty good speakers. I replaced mine with the Oberon 7s but that is a bit of a budget jump From what you have suggested. Only one way to find out though.