Super S brake discs upgrade

hey guys!

So, facebook group members may know me as Galaxy Boy xD

I own a Super S whose brakes feel like butter! So I'm thinking of upgrading. I know I can bolt in N14's brakes, but I want to start with something more simple. The plan is to put some vented front discs and better quality pads.

now, I've been told I run 234mm discs. Problem is that the best quality are 238mm vented discs. Will those fit on the standard caliper? Or will I have to get new ones? And if I do, will the fit my 13 inch wheels? (if I have to get the calipers, I'll probably go for the N14's then...)

what is the best option? What would you do?