I went from a Project Debut 3 SE to a Rega RP3, definitely a step up in performance but no where near the improvement that I got from changing the cartridge that it came fitted with.
The original cartridge was an OM10 which I didn't get on with at all. An Ortofon 2m Blue made a big difference in terms of detail and clarity and shows what the Debut 3 SE was capable of. However , I found the Blue to be rather too clean, almost CD like so I changed it for a Nagoaka MP110. This cartridge is more warm/analogue sounding if not quite as detailed as the Blue. I then swapped the MP110 stylus (not the body) for the one fitted to the MP200 and I now get the best of both cartridges.
If you have the OM10, then a cartridge change will give big improvements!
The Debut 3 SE is more than capable of matching the Rega P2 I believe, f you just want a change, why not try fitting an acrylic platter - looks great against that gloss black plinth.