My 9 year old Project Debut II - how can I improve it?

I don't know what stylus I am using it but I think it may be an Ortofon professional from the days when I used to do DJ practice but the cartridge is from an OM10.

I love its musical presentation and I find they suit my Warfedale 9.1s better than Marantz CD6000 OSE OE which seems a little bright for them. I am currently listening to my old Morrissey/Smiths and it sounds really musical but I can't help feeling so is so much detail missing but maybe this why it sounds so good?

Anyway what upgrade can I do it to keep its same musicality but add some detail? A new belt? A new Ortofon cartridge? Will any shops set it up for me if I bought a completly different cartridge?

Given the poor quality of the built in arm I can't see many options really. I don't want to change my turntable as its the only original seperate I have left so it has a place in my heart.