To keep, upgrade or change

Hi all,

New to here, got back into playing my vinyl and so have a setup that was purchased quickly just so I could start listening again

I have a Marantz KL Pearl Lite Amp with Wharfdale Diamond 10.2 speakers

But my current turntable is a little bit of a hybrid, it's an Aiwa badged Rega plinth, and motor Debut tone arm with a Ortofon OMcart with a Thakker 10 stylus.

Now my question is, should I keep, or upgrade the motor and then later on the arm and stylus. Or should I cut my losses and go for a Rega Planar 3 with better arm etc and get the stylus/cart?

Currently very happy with the sound very clear etc but there's always that 'what if I did....'

Based on recent experience, be very careful when approaching change in your system. I purchased a new integrated and wasn’t happy with it but it also lowered my satisfaction with my original system. In the end, I did pick up yet another amplifier that I absolutely love so all is well. I would suggest going for a completely new component that you can A/B rather than having to physically take it apart for the upgrade. 
I recommend a Pioneer PLX1000 TT. $700. Direct drive. Add the latest Grado MI cartridge ($100 - 200) and you will have a fine sounding system. Later, you can upgrade to an MC cartridge (Denon, Hana ...).
Thanks for the replies, I have purchased a cork mat and glass platter to try out, this was I thought I could slowly changes things which then would mean not a big leap.

As mceljo said, I thought making small changes that could be reversed.