duet comes with it's own stepper drivers - stepper motors are (more or less) fairly standard.

Love the fact that you bought a cheap printer replaced: (bearings, belts, power supply & mosfets) and then claim it pints really well 'as is' for a cheap machine. Irony is that.
The duet alone is almost twice what you paid for the original machine. Which - for the record - is an Anet a8 - w5 model.

having just bought a similiar machine (ctc 13 pro b), I know the appeal of the initial cheapness. I'm approaching from a different angle and intedn to see how well i can get it working with just printed mods.
But if you add up what you initially paid - throw in ?150 for the duet and add up all the extras you've bought - then look at the machines in THAT price range. It's kinda counter-productive.
You've got to be looking at ?250 plus. Which would have gt you a printer with a rigid aluminium frame and all round better components that probably wouldn't have needed replacing.

As far as benefit for the duet versus the mks - and ignoring the ?110 price difference - yes the duet will give you better performance. Even with bog standard stepper motors, the drivers on the duet will make a significant difference. PLus it's got wifi and the guys who make the duet are really great people and do exceptional support for their products.

I'll be meeting them at tct in a few days - fascinated to see what they've built a duet into this year. last year they had a 6 extruder machine and a couple of really cool deltas.

If only they weren't so bloody expensive :-)